Briggs, R. P. (1977). Environmental geology, Allegheny County and vicinity, Pennsylvania: Description of a program and its results. US Geological Survey.
Chicago-Zitierstil (17. Ausg.)Briggs, Reginald Peter. Environmental Geology, Allegheny County and Vicinity, Pennsylvania: Description of a Program and Its Results. Arlington, Va: US Geological Survey, 1977.
MLA-Zitierstil (9. Ausg.)Briggs, Reginald Peter. Environmental Geology, Allegheny County and Vicinity, Pennsylvania: Description of a Program and Its Results. US Geological Survey, 1977.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.