TY  - RPRT
TI  - A portable vacuum hammer seismic source for use in tunnel environments
AU  - R. D. Carroll
AU  - J. E. Magner
PY  - 1993
DO  - 10.3133/ofr93187
UR  - https://pubs.usgs.gov/publication/ofr93187
ID  - ofr93187
ER  -