Author
- American Chemical Society. Cellulose, Paper, and Textile Division 1 results
- Brandywine Valley Association 1 results
- Brinkley, Douglas 1 results
- Clepper, Henry, 1901-1987 1 results
- Forest History Society 1 results
- Freeman, Orville L. 1 results
- Frome, Michael 1 results
- Hopkins, Alix W. 1 results
- Indian Education Resources Center. Branch of Curriculum 1 results
- Koelsch, William A. 1 results
- Maunder, Elwood R. 1 results
- Mitchell, Lee Clark, 1947- 1 results
- Natural Lands Trust 1 results
- Nature Conservancy (U.S.) 2 results
- Pennsylvania Audubon Society 1 results
- Pennsylvania Land Trust Association 1 results
- Pennsylvania. Bureau of State Parks 1 results
- Pennsylvania. Department of Conservation and Natural Resources 1 results
- Pennsylvania. Office of State Planning and Development 1 results
- Pennypack Watershed Association 1 results
- Philadelphia Conservationists, Inc 1 results
- Philadelphia Record 1 results
- Rosenkrantz, Barbara Gutmann 1 results
- Ruppert, Estelle 1 results
- Sierra Club 1 results
- Sierra Club Pennsylvania Chapter 1 results
- Sierra Club Southeastern Pennsylvania Chapter 1 results
- Speakman, Joseph M., 1940- 1 results
- Steidle, Edward, 1887-1977 1 results
- Williams, John Covington, 1911- 1 results