"Specifications of the labor and materials required for the construction of the street railway tunnel and its approaches between Twenty-Third Street and Spring Garden Street Bridge for the Commissioners of Fairmount Park with instructions to bidders, general conditions of the contract, form of proposal and acceptance", circa 1923

"Specifications of the labor and materials required for the construction of the street railway tunnel and its approaches between Twenty-Third Street and Spring Garden Street Bridge for the Commissioners of Fairmount Park with instructions to bidders, general conditions of the contract, form of proposal and acceptance", circa 1923, Box: 9, Folder: 15. Archives Reference Files, REF. Philadelphia Museum of Art, Library and Archives. https://pmalibrary.libraryhost.com/repositories/3/archival_objects/227869 Accessed June 01, 2024.