TY  - RPRT
TI  - 3D-DEF; a user's manual (a three-dimensional, boundary element modeling program)
AU  - J.S. Gomberg
AU  - Michael Ellis
PY  - 1993
DO  - 10.3133/ofr93547
UR  - https://pubs.usgs.gov/publication/ofr93547
ID  - ofr93547
ER  -