^"Species". Napa Valley Register. Napa, California. 2020-04-17. p. B3.
^United States Geological Survey (1952). "Liberty Island Quadrangle, California" (Map). United States Department of the Interior Geological Survey. 1:24000.
^United States Geological Survey (1978). "Liberty Island Quadrangle, California" (Map). United States Department of the Interior Geological Survey. 1:24000.