TY  - BOOK
AU  - Obert Leonard
AU  - Duvall W I
TI  - Micro-seismic method of determining the stability of underground openings
U1  - 551.22 
PY  - 1957///
KW  - Geology
KW  - Seismology
N1  - photo-print from US Bureau of Mines, Bull. 573, 1957
ER  -