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By Stephen C. Tadolini, Colton Cook, Cody Hildreth, Frederick Cybulski

"Broken and jointed ground is extremely hazardous and requires unique stabilization techniques to protect worker and critical entries. Bolting techniques, even the most advanced with pre-load to create roof compression, can leave large gaps of unconfined and separated roof. This roof can also be susceptible to water inflows which only exacerbate the support problem. These types of conditions existed on long term development main entry accessing several future longwall panels. The geotechnical assessment identified well-defined jointing systems that also permitted water to flow between the roof separations, which “lubricated” the roof material and minimized any frictional advantages. Chemical injection of a Polyurethane material, Minova Carbopur WS, was placed beyond the bolted horizon to move the water to the rib lines and reinforce the fractured and broken roof. The injection material permitted the effective use of bolting patterns and helped ensure long-term stability of these critical entries. The paper describes the evaluation techniques, design patterns, basis for chemical selection and application, and results and recommendations.BACKGROUNDThe injection of mine and underground civil structures using polyurethane (PUR) has been ongoing for over 50 years. The applications in mining have included gate road stabilizations, longwall set-up and tear-down entries, and simple consolidation of coal mine roofs. PURs have also been used for roof stabilization during longwall shield recoveries. Polyurethane injection was initially developed by the Bergbau-Forshung GmbH, a German coal mine research institute, in the early 1960s (Jankowski, 1972). The product became a standard stabilization method in Germany after its commercial introduction in 1971 (Knoblauch, 1994), and was successfully manufactured at the Minova Essen, Germany location for over 50 years. With the recent closing of the German underground mines, that manufacturing facility has been closed and moved to Katowice, Poland, where production continues today Injection products are also being successfully manufactured by Minova in Australia and the United States.Polyurethane injection in underground coal mines is used in difficult ground conditions in fractured immediate and main roofs. It is also common as a rock stabilization remedy to prevent longwall face caving during shield removal. As presented in the case study, polyurethane was applied to minimize the inflow of water from beneath a stream channel while providing reinforcement and consolidation of the fractured roof that had lost confinement. Polyurethane is a two-component system (Part A and Part B) that is injected into a borehole and can chemically bond to the rock, not relying on friction or mechanical interlock to provide support. The material is injected under pressure, coupled with a low viscosity and small particle size; it flows into roof fractures and separations, which are the paths of least resistance. New developments in low viscosity PUR materials allows penetration of cracks as tight as 0.002 inch (0.05 mm) wide. This also allows for the closures of extremely small cracks to minimize the inflow of water, even if the water is under pressure. Combinations of designed expansion properties and low viscosities make the materials ideal for minimizing and stopping flows of water from underground structures."

Jan 1, 2019

By R. A. Beall

Consumable-electrode arc melting is now accepted throughout the industry as the best method for producing ingots of zirconium, titanium, molybdenum, and their alloys. In addition, the technique is widely used in laboratories for fusing samples of such metals as hafnium, chromium, tantalum, columbium, and thorium. The production of consumable electrodes from these metals presents some rather difficult problems, the accepted industrial solution being the use of heavy powder-metallurgy-type presses. This paper summarizes information on fabrication of consumable electrodes by this and alternative means, such as sintering, nippling, and welding lightly pressed compacts of scrap metal. A possible saving of considerable capital investment is shown in the case of sintered compacts. The electrical circuit components of a pilot sintering unit are analyzed. INTRODUCTION The consumable-electrode arc-melting process has been accepted by most of the industry as the best method at present for producing high-quality pure or alloy in-got from sponge titanium or zirconium. This technique is not particularly new, having been patented by Von Bolton (l)3/ in 1909 for melting tantalum. However, it has been applied to industrial-scale operation only in the last few years. Among the important contributions to this technique are the work of Kroll (2) and Parke and Ham (3) and the work reported by the Office of Naval Research (4). The Bureau of Mines-has added considerably to the knowledge of this process (5-9).

Jan 1, 1956

By Hillary W. St. Clair

Mining activity began in colonial times with ironmaking operations scattered along the eastern seaboard. Iron furnaces and forges manufactured iron implements from bog iron ores using charcoal from the extensive forests as a fuel. Lead ores were mined in the Mississippi Valley and copper ores in the Lake Superior region. However, the real beginning of the American mining industry did not occur until the 19th century. The history of American mining is organized around three epochal events. The first was the discovery of gold in California in 1848, which marked the beginning of a period of apprenticeship in mining and metallurgical techniques. The second was the discovery of the fabulous Comstock Lode in western Nevada in 1859, which expanded mining throughout the Far West and led to large-scale underground mining and the development of smelting techniques for lead, silver, and copper ores. The third event was the building of a transcontinental rail-road system after the Civil War, which brought about the consolidation of the industry from a large number of independent mines, mills, and smelters into integrated operations run by large corporations. Thus developed the mining industry that today supplies the energy and critical materials for the great-est industrial complex the world has known.

Jan 1, 1977

By D. Gu, R. G. Anthony, C. V. Philip, M. E. Huckman

"In this paper, we review the equations needed to construct an ion exchange column model. These models contain three major components: 1) a differential material balance around the column, 2) a differential material balance around an ion exchange particle, and 3) a constitutive equation for diffusive flux. We then examine the ability of a fairly simple mathematical model to predict ion exchange column experimental data. This model contains the traditional absorption theory equations and is used to predict the behavior of a column filled with a hydrous crystalline silico-titanate and which is removing trace amounts of Cs+ from a high pH, complex electrolyte solution. Finally, we propose replacing Fick's law with the Nemst-Planck equation as the constitutive equation for diffusive flux. We use a NemstPlanck type model to predict batch experimental data, then evaluate it by comparing it's ability to predict experimental data to that of a more traditional Fick's law type model. The data from this comparison suggests that the Nemst-Planck type model yields better results.IntroductionMillions of gallons of strongly basic, radioactive waste are currently stored in underground storage tanks at Hanford and Savannah River and several locations within the United States. Due to the limited life expectancy of the tanks, there is a pressing need to remediate these wastes. This need has prompted the recent development of new ion-exchange materials for removing radioactive elements from aqueous solutions. A novel material called TAM-5 has been developed jointly by Texas A&M University and Sandia National Laboratories. TAM- 5, a crystalline silico-titanate, is highly selective for Cs + in the complex electrolytic solutions typical of these wastes. It is stable in very basic solutions and in radioactive environments [1, 2 ,3]. In laboratory testing to determine the selectivity of various materials, TAM-5 was superior to other candidate ion exchangers [4, 5]. The selectivities were determined by measuring a distribution coefficient, Kd, which is defined as the concentration, gig or mmols/g of Cs in the solid phase divided by the concentration, mg/L or mmols/mL, of Cs in the liquid phase. The units of Kd are ml/g or L/kg. Table 1 shows Kd values for TAM-5 compared to 9 other candidate materials in a typical waste solution [6]."

Jan 1, 1996

By M. Rahmanpour

"Mine planning is a multidisciplinary procedure that aims to guarantee the profitability of a mining operation in changing and uncertain conditions. Mine plans are normally classified as long-term, intermediate-term, and short-term plans, and many factors affect the preciseness of these plans and cause deviations in reaching the objectives. Commodity price is the heart of mine planning, but it has a changing and uncertain nature. Therefore, the determination of mine plans in the presence of uncertain mineral price is a challenge. A robust mine plan reduces the risk of early mine closure. A procedure is presented to determine the value at risk (VaR) in any possible mine planning alternative. VaR is considered together with downside risk and upside potential in order to select the most profitable and least risky plan. The model is tested on a small iron ore deposit. IntroductionMining projects are normally evaluated with the objective of maximizing economic value, as measured by the net present value (NPV). The aim of mine planning is to develop a yearly extraction plan that guides the mining operation to the highest NPV (Dagdelen, 2007; Yarmuch and Ortiz, 2011). This plan considers the technical constraints such as blending requirements, block sequencing, and pit slope (Caccetta and Hill 2003). Thus, the mine plan affects the economics and the payback period of mining operations.Mine planning is a procedure based on which the profitability of the mining operation is guaranteed in changing and uncertain conditions (McCarter, 1992). However, conventional mine planning ignores the volatility and uncertainty of future commodity prices and does not allow for managerial flexibility. It is common practice to assume a deterministic and constant commodity price through the mine life. The problem with this approach is that the commodity price is the heart of the mine planning procedure and governs the profitability and feasibility of the operation; thus ignoring price volatility will result in a sub-optimal mine plan."

Jan 1, 2016

Underground coal mine tracked vehicles have been studied to determine the state of the art and how brakes might be added to the coal haulage cars. Specific areas of interest are: brake sys terns, couplers, car trucks and car handling procedures. Problems related to adding brakes to the haulage cars appear to be: the limited amount of room to mount the brakes on the cars, brake line connection between rotary dump cars, achieving desirable braking characteristics without over complicating the system and keeping the installation cost to a reasonable figure. This document combines the information contained in the first issue of the "State-of -the-Art of Underground Coal Mine Tracked Vehicle Brake Systems," BRL Report No. 6080, with that contained in a subsequent monthly report.

Jan 1, 1973

By R. Tervo, G. Ellie

"Automated information systems are being developed very rapidly in Europe. In France, Belgium and West Germany, more than 70% of the coal production is controlled by these installations. Information on both product ion and the mine environment is produced. For example, at one mine in France the system records the operating times of the compressors and of the refrigeration pumps, counts the number of coal cars passing the unloading point, and controls the principal conveyors and the loading /unloading of the storage bins. In addition, the ventilation air velocity, the methane content and the carbon monoxide content in the return air entry are recorded; an alarm is triggered and the current to the conveyors cut when the gas content exceeds a critical level. The recorded information is used at four levels: (1) for immediate action, (2) for daily reports, (3) for monthly reports and (4) for long-term studies. For example, when any conveyor is stopped for more than 10 minutes, the system controller immediately telephones to learn of the reason. At the end of a shift, the load factor of the conveyors is computed; then monthly an analysis of the causes of low load factors is made. The presentation describes in detail the system that has been installed in more than 20 mines in France."

Jan 1, 1973

By Leon W. Dupuy

Marquette's first reported the existence of iron In Missouri in 1673. Recorded production wan begun in 1815, increasing in size and importance until 1888, when the low price of iron resulting from Minnesota's production of high-grade ore caused most of the operators to close down. Missouri's iron production came from three types of ore: (l) Brown ores, including the deposits of primary and secondary limonites in southeast and southwest Missouri, (2) hematites of the filled sinks, including the ores of Central Ozark district, and (3) specular ores in porphyry, including the deposits of the St. Francois Mountains.

Jan 1, 1949

By McKee D. J

Much research is aimed at providing a revolutionary advance in technology that has the potential to render current mining and beneficiation problems obsolete. Such revolutionary advancements have been significant but few in number. Recent history shows that most improvement has been derived from a series of incremental improvements to the many processes that make up mining and beneficiation systems. Management approaches are changing to encourage this 'continuous improvement' and to support its implementation through the formal management of quality. This paper reviews some of the industry's priority R&D project areas and demonstrates that very significant opportunities are available to broaden the focus for improvement from individual processes to include the interaction between mining and mineral beneficiation systems.

Jan 1, 1994

By Oliver Bowles

The Bureau of Mines issued three Information Circulars on marble many years ago (5), (6), (7).2/ They have long been out of print; furthermore, conditions have changed considerably in the industry in succeeding years. A presentation of current data is therefore desirable. This report furnishes general information on marble, including its properties, distribution of domestic and foreign deposits, methods and equipment used in quarrying and milling, economic and marketing problems, and recent advances in marble technology. INTRODUCTION Most marbles are crystallized limestone. The term "marble" is derived from a Greek word meaning to sparkle or flash, because the calcite crystals in marble sparkle as they reflect light. The word "marble" is employed frequently to mean a small ball used in the game of marbles with which nearly every child is familiar. Although the little spheres were originally of marble, few of those made in recent years contain that material; nevertheless, the expression "playing marbles" has persisted.

Jan 1, 1958

By P Audet, D Doley

The mining industry often embraces mine closure criteria that require the reinstatement of predisturbance or even presettlement (ie historic) ecosystems. However, the extent and severity of disturbance associated with most mining activities mean that critical physical and biological characteristics are irreversibly altered. Consequently, it is rare that a reconstructed landscape can support ecosystems even close to the historic condition, and this rarity is reflected in the small number of mine leases that have been extinguished by attainment of such completion criteria. Novel ecosystems are defined as those in which some or all physical and biotic components are irreversibly different from the historic condition. Recognition of the concept of novel ecosystems allows mine closure criteria to be set according to attainable physical and biological conditions that provide safe, stable and manageable environments with acceptable ecological functions. We propose that a landscape that first maximises physical stability and economy yet will provide a range of environments for vegetation communities and fauna habitats that may be very different from those existing prior to a disturbance should be considered suitable alternatives to, eg targeting idealised historic environments. As a result, mine closure criteria should be established by detailed description of the best attainable physical conditions, with negotiated identification and testing of the most appropriate biological systems for the various parts of the reconstructed landscape. As a general practice, revegetation would use native, but not necessarily local species if the new physical environment is not conducive to the survival and growth of local species. These new ecosystems would need to be managed in perpetuity, although the intensity of management might be low if landscape design and engineering are combined with appropriate species introductions. Here, we suggest an abbreviated procedure that may be adapted in light of local conditions and circumstances for guiding decisions influencing the physical and biological properties of reconstructed landscapes that will enable novel ecosystems to meet realistic closure criteria.CITATION:Doley, D and Audet, P, 2014. Changing restoration priorities in the 21st century – opportunities for novel ecosystem design in mine closure, in Proceedings Life-of-Mine 2014 , pp 649–662 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By David G. Kidd

The principles of Ore Sorting in general and photometric sorting in particular are discussed with detailed reference to the Model 16 machine. The operating principles and design of the Model 16 are discussed and a case study presented to demonstrate the use of sorters to process an industrial mineral. In addition, an economic study is presented, to highlight the benefits of ore sorting, by evaluating the increased revenue that can be achieved using an ore sorter to process a particular ore body.

Jan 1, 1983

By P. G. Dempsey, J. R. Heberger, J. P. Pollard

During a mine disaster or emergency, underground air can quickly become contaminated. In these circumstances, all underground mine workers are taught to don breathable air supply units at the first sign of an emergency. However, no contemporary oxygen consumption data is available for the purposes of designing breathing air supply equipment specifically for mine escape. Further, it would be useful to quantify the oxygen requirements of breathing air supply users for various escape scenarios. To address this need, 14 participants crawled a distance of 305 m each while their breath-by-breath oxygen consumption measurements were taken. Using these data, linear regression models were developed to determine peak and average oxygen consumption rates as well as total oxygen consumption. These models can be used by manufacturers of breathing air supply equipment to aid in the design of devices that would be capable of producing sufficient on-demand oxygen to allow miners to perform self-escape.

Jan 1, 2015

By John F. Beesley

INTRODUCTION This paper discusses the design of the subsurface nuclear waste repository at Yucca Mountain, Nevada; and possible concepts for construction of the subsurface facility. Subsurface construction at Yucca Mountain is planned to last for 20 or more years, and may be accomplished using tunnel boring machines (TBM), drill and blast methods, raise bore machines, and roadheaders. The design of the subsurface facility includes approximately 107 km (66 miles) of tunnels and drifts. The vast majority of the repository will be excavated with TBMs. Design and construction concepts for the subsurface repository discussed in this paper are based on the License Application that was submitted to the U.S. Nuclear Regulatory Commission (NRC) by the U.S. Department of Energy (DOE) on June 3, 2008. The License Application was subsequently docketed by the NRC in September 2008. When a Construction Authorization is received from the NRC, notices to proceed with subsurface construction at Yucca Mountain will be issued by DOE. The Yucca Mountain site is located in the Mojave Desert approximately 150 km (90 miles) northwest of Las Vegas, Nevada. The site is on federal land in southern Nevada and is shown in Figure 1. Yucca Mountain is a ridge of volcanic rocks com-posed primarily of solidified volcanic ash. Previous underground construction work at Yucca Mountain included excavation of two tunnels using two different TBMs. The first tunnel, the Exploratory Studies Facility (ESF), is a 7.62 m (25 ft) diameter tunnel that is 7,877 m (25,843 ft) long and was described by Morris and Hansmire at the Rapid Excavation and Tunneling Conference (RETC) in 1995. The second tunnel, known as the Enhanced Characterization of the Repository Block (ECRB), was a TBM drive of 5.0 m (16 ft, 5 in.) in diameter and 2,681 m (8,796 ft) long. The second tunnel was excavated in 1998 and was described by Fulcher, Eastlund and Copeland at RETC 1999 and is named the East?West Cross Drift in that paper. (These previously excavated tunnels are shown in Figure 2.) In the volcanic rock formation where the vast majority of the planned repository will be con-structed, previous tunneling conditions were generally very good.

By M Hawkins

The Clem Jones Tunnel (formally known as the North-South Bypass Tunnel), a A$2.88 billion road tunnel project in Brisbane, Queensland, was successfully completed almost seven months ahead of schedule. The project included two parallel 4.7 km long road tunnels, 740 m of intermediate roadway access ramps and two auxiliary ventilation tunnels. The tunnels incorporate intelligent tunnel systems, best practice fire and life safety standards and typical civil tunnel elements.Over the duration of the project the Parsons Brinckerhoff (PB) and AECOM (formally Maunsell) design joint venture (MPB) were Lead Designers to the Leighton Contractors and Baulderstone Bilfinger Berger Joint Venture (LBBJV). Construction of the toll road commenced in September 2006 and was completed in March 2010, with the tunnel opening then. Contributing to the success of this project was the continued support the lead designers gave throughout the construction period.This paper will focus on some of the structural elements that contributed to the success of the project – in particular the cable tunnel structure, a small precast, culvert shaped element under the pavement of the mainline tunnel, and the fit-out of the Gibbon Street shaft which were designed to be constructed in a combination of precast and in situ concrete.The cable tunnel was incorporated early in the design phase and runs the length of much of the tunnel. This paper will outline the challenges faced by the designers with implementing this system which provided significant construction advantages, among which were being able to install a separate ventilation duct during construction and to start fitting out the mechanical and electrical conduits and drainage system while tunnelling was still underway.The Gibbon Street shaft had a length and width of 20 m by 40 m and an overall depth of 38 m. A 20 m high structure of precast and in situ concrete was constructed in the base to accommodate mechanical and electrical equipment and provide a take-off access for the southern ventilation tunnel. The construction purpose for this structure was to provide a junction between the tunnel boring machine (TBM) and the roadheader-style tunnels, a staging platform for commencing the roadheader tunnelling, and a platform where the TBMs could be dismantled and removed.The design was assessed and reviewed many times throughout the construction process to address the needs of each of these stages. Innovative use of precast concrete was used to minimise construction time.Additionally, the designers provided support to the construction team from the time of design completion through to the tunnel opening. This meant that the changes to the design and adjustment of construction loadings could also be assessed. The fi nal outcome resulted in an efficient construction sequence and a project that has provided an excellent outcome for the client, stakeholders and community.

Mar 8, 2011

By R Adamian, F. T. Da Silva, D. H. Gameiro

Schytill and Geldart diagrams were developed for the TiO2-C-Cl2 system at 1 073 and 1 273 K, so as to define the hypothetical relations between particle sizes and chlorine velocity for simultaneous fluidisation of mixtures of anatase concentrate and charcoal for carbochlorination. It was concluded that the operating limits on chlorine gas velocity will be controlled by the behaviour of the reducing agent, mainly because of its lower density. An increase in temperature from 1 073 to 1 273 K will have only a small influence on the fluid-dynamic behaviour of the mixture. For bubble fluidisation, the maximum sizes 0.413-0.478 mm for anatase and 0.529-0.611 mm for charcoal will be adequate. When the particle size distribution is large, fluidisation will be feasible only if conducted in two stages, otherwise the residence time of the small particles in the reactor will be very short. New diagrams will be needed for the gaseous chlorides in the second stage

Jun 21, 1905

By F. W. Lee

List of GEOPHYSICAL ABSTRACTS

Jul 1, 1932

By F. E. Cash

"Explosions in bituminous coal mines are preventable. The combination of adequate ventilation, thorough rock-dusting, and water on the cutter bars of mining machines and of empty and loaded cars will certainly reduce the hazard to a minimum, if not remove it entirely. This is the attitude taken by the Woodward Iron Co. in lessening or removing the dust and gas explosion hazard from its Dolomite and Mulga mines.This report was made possible through the willingness of Frank H. Crockard, president of the Woodward Iron Co. to make records available and to authorize their publication for the benefit of the coal-mining industry.The compilation of these data and preparation of maps was facilitated by the cooperation of M. Heard, general superintendent of coal mines, J. B. Whatley, assistant general super-intendent of coal, and R. P. Whetmore, chief mining engineer.The Dolomite and Mulga mines are about 16 miles southwest of Birmingham, Jefferson County, Ala., on a company owned and operated railroad which connects ore mines, coal mines, coke ovens, and furnaces.In the Dolomite property there is a 30°, 860-foot, double-tracked slope for hoisting, three manway and air slopes and one air shaft, all in rock.At Mulga there is a 220-foot hoisting shaft, an air shaft and two manways, and material and air slopes, all in rock to the coal bed.The coal in both mines comes from the Pratt bed, which is the next coal above the Mary Lee bed in the Warrior Basin. The coal is horizontal or slightly undulating, with thickness varying from 36 to 72 inches and averaging 50 inches.The method of mining is essentially room-and-pillar with modifications for mechanized sections. The mines produced approximately 1,100,000 tons with 2,328,309 man-hours exposure n 1929 and 900,000 tons with 1,697,436 man-hours exposure in 1930.Through the work of the safety department the entire personnel in the coal mines, as well as in other departments, makes safety an essential part of efficient operation.Both mines are gassy; Dolomite produces about 334,000 cubic feet and Mulga about 919,000 cubic feet of methane every 24 hours.The ventilation maps, two of Dolomite mines (figs. 1 and 2) and one of Mulga (fig. 3) give as much of the details of ventilation as is practicable to put on maps of such scale. As will be seen from these maps there are two main ventilating fans in Dolomite mine and two in Mulga mine and the general direction of the air travel is indicated by long arrows to fan 1 and short arrows to fan 2 in each mine. Each fan has a gas or steam auxiliary drive and each mine has a complete fan and power unit ready for operation in emergency.In Dolomite, recently taken data show that fan 1 exhausts 82,000 cubic feet of air per minute at 3.2-inch water-gage pressure, with an analyzed methane content of 0.15 per cent, and fan 2 exhausts 115,500 cubic feet of air at 3.8-inch pressure and 0.10 per cent of methane. In addition, a Capell fan at No. 2 air shaft is a standby or emergency unit.In Mulga recently taken data show that fan 1 exhausts 83,000 cubic feet of air per minute at 3.0-inch pressure and 0.18 per cent of methane, and fan 3 exhaust 119,000 cubic feet of air per minute at 5.4 inch pressure and 0.35 per cent of methane. Fan 2 at No. 2 shaft is a standby or emergency unit for the Mulga mine.The ventilation is on a split system in both mines. All part split and total returns are measured, sampled, and analyzed weekly, requiring one man two days each week. During December, 1930, 77 samples were collected and analyzed in Mulga and 78 in Dolomite. Two weekly reports covering part of December, 1930, are given here so that they can be studied to show control of ventilation in the Dolomite and Mulga mines. In the event that a split sample shows more than 0.50 per cent of methane, immediate steps are taken to lower the explosive-gas content. The reports follow:"

Mar 1, 1932

By S. L. Chen

The Kumera Technology Center developed a unique type of steam dryer for drying copper concentrate in the mid 1990s. The dryer has been chosen in several copper smelter projects since 1999. To expand production capacities, the Norddeutsche Affinerie smelter, the Pirdop smelter of Cumerio, the Toyo smelter of Sumitomo Metal Mining and the Tamano smelter of Hibi Kyodo Smelting have carried out projects in which Kumera Steam Dryers were installed. The capacity of a single steam dryer varies from 70 t/h to 160 t/h. This article summarizes the latest operation results of the Kumera Steam Dryers in these smelters and introduces the progress of the ongoing projects in Yanggu Xiangguang Copper, Guixi smelter of Jiangxi Copper, Jinlong Copper, Boliden Harjavalta, and Onsan smelter of LS-Nikko Copper.

Jan 1, 2007

By P. F. Mataich

"Why bother with computer control?" This question and others like it have been heard over and over again by those who have tried to convince operating men that there are sound merits to installing a process control computer. At IMC we have done a great deal of thinking and talking about computer control. In the course of these discussions the operating people have asked a number of questions about computer control. These questions and our answers to them make up the main part of this article. Obviously, the answer as to whether or not to go into computer control will be an individual problem conditioned by your company's circumstances. What I hope to do here is raise some questions, give you an idea of our thinking on the subject, and lay out some general guidelines for you to consider.

Jan 1, 1965