TY  - RPRT
TI  - A generalized finite-difference formulation for the U.S. Geological Survey modular three-dimensional finite-difference ground-water flow model
AU  - Arlen W. Harbaugh
PY  - 1992
DO  - 10.3133/ofr91494
UR  - https://pubs.usgs.gov/publication/ofr91494
ID  - ofr91494
ER  -