scientific article published in 1955

scientific article published in 1974

scientific article published in May 1981

scientific article published in 1986

article

scientific article published on 15 July 2003

[Washington]: National Park Service: may be purchased from the Supt. of Docs., Govt. Print. Off., 1975.

scientific article (publication date: August 2002)

scientific article published on 13 April 2006

scientific article published on 25 April 2006

scientific article published on 20 August 2010

scientific article published on 12 March 2003

scientific article published on 01 July 2005

scientific article published on 26 April 2006

scientific article published on 15 December 2016

scientific article published on 07 April 2006

scientific article published in 1981

scientific article

scientific article published on 25 April 2006