Reed, John C. 1930- Crystalline rocks of the Potomac river Gorge near Washington, D.C. / by John C. Reed and Janice Jolly. -- Washington : United States Government Printing Office, 1963 - 16 p. -- (Geological Survey Professional Paper ; 414-H). Subjects--Topical Terms: PetrologíaRocasWashington Universal Decimal Class. No.: 552(797)