Bureau Historian (2006). "Former National Park System Units: An Analysis" . National Park Service. "National Monument Proclamations under the Antiquities Act" National Park Service Office of Public Affairs (2009). "UNITS & RELATED AREAS & RELATED AREAS IN THE NATIONAL PARK SYSTEM". Last updated January 13, 2017. (Lists 317 NPS units and related areas by classification).
bUreAU HistorIan (2006). "FORmer NatIoNAL Park system unIts an aNalysiS" . nationaL pArk SErvICe. "naTioNal moNumeNt PROclAmations undER the antiquitieS acT" natioNal park SErviCE oFfice oF Public affAirs (2009). "uNITS & related aReas & rELAted AreaS in thE natIoNaL parK syStEm". last upDated jAnuary 13, 2017 (ListS 317 nPs uniTs And relATeD AREas by ClasSIfiCaTIon).