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1by Harper, John A.“... and Engineering Services, Bureau of Topographic and Geologic Survey and Bureau of State Parks,...”
Published 1998
Book -
2by Braun, Duane D.“... and Engineering Services, Bureau of Topographic and Geologic Survey, Office of Parks and Forestry, Bureau of State...”
Published 1998
Book -
3by Faill, Rodger T.“..., Bureau of Topographic and Geologic Survey and Bureau of State Parks ; State of Delaware, Delaware...”
Published 1991
Internet Archive, State Library of Pennsylvania
Government Document Book