TY  - RPRT
TI  - Aeromagnetic map of the Billerica quadrangle, Middlesex County, Massachusetts
AU  - Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey
PY  - 1971
DO  - 10.3133/gp743
UR  - https://pubs.usgs.gov/publication/gp743
ID  - gp743
ER  -