APA (7th ed.) Citation

Helfrich, C. T. (1977). Geologic map of the North Middletown quadrangle, east-central Kentucky. U.S. Geological Survey.

Chicago Style (17th ed.) Citation

Helfrich, Charles T. Geologic Map of the North Middletown Quadrangle, East-central Kentucky. Reston, Va.: U.S. Geological Survey, 1977.

MLA (9th ed.) Citation

Helfrich, Charles T. Geologic Map of the North Middletown Quadrangle, East-central Kentucky. U.S. Geological Survey, 1977.