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The American Institute of Architects Archives
Architects Roster questionnaire, 1946, contains information about the firm and its key personnel. (Note-large pdf, 26MB)
University of North Texas Special Collections
David S. Castle Architectural Drawings Collection, 1914-1962
Finding aid to the collection is available at https://findingaids.library.unt.edu/?p=collections/findingaid&id=877. Digitized drawings are available through the Portal to Texas History https://texashistory.unt.edu/explore/collections/DVDCAD/
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