(1976). Geologic map of the Avella Quadrangle and part of the Steubenville East Quadrangle, Washington County, Pennsylvania. U.S. Geological Survey.
Chicago-Zitierstil (17. Ausg.)Geologic Map of the Avella Quadrangle and Part of the Steubenville East Quadrangle, Washington County, Pennsylvania. Reston, Va: U.S. Geological Survey, 1976.
MLA-Zitierstil (9. Ausg.)Geologic Map of the Avella Quadrangle and Part of the Steubenville East Quadrangle, Washington County, Pennsylvania. U.S. Geological Survey, 1976.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.