February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index

This Bureau of Mines publication reviews the research conducted under a 3-year, $6.6 million program in rock mechanics and rapid excavation. The program was sponsored by the Defense Department's Advanced Research Projects Agency and was managed by the Bureau. In addition to the rock mechanics investigations, projects were funded in the following general areas of rapid excavation: System analysis, geologic prediction, rock disintegration, ground support, and materials handling. This report briefly summarizes the significant technical accomplishments of the individual research projects and references the contract reports and other publicatons where more detailed descriptions of the research can be obtained.