Não informado. (1949). Historic preservation. National Trust for Historic Preservation.
Chicago-referens (17:e uppl.)Não informado. Historic Preservation. Washington: National Trust for Historic Preservation, 1949.
MLA-referens (8:e uppl.)Não informado. Historic Preservation. National Trust for Historic Preservation, 1949.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.