APA (7th ed.) Citation

Geological Survey (U.S.). (1986). Index to USGS topographic map coverage of national park system, October 1, 1986. The Survey.

Chicago Style (17th ed.) Citation

Geological Survey (U.S.). Index to USGS Topographic Map Coverage of National Park System, October 1, 1986. Reston, Va.: The Survey, 1986.

MLA (9th ed.) Citation

Geological Survey (U.S.). Index to USGS Topographic Map Coverage of National Park System, October 1, 1986. The Survey, 1986.