Fletcher, Sydney E.
Grosset & Dunlap, 1954
Buku Teks
Epps, Garrett
Oxford Univesity Press, 2013
Buku Teks
Wilson, Eva, 1925-
British Museum, 1998
Buku Referensi
Iverson, Peter
West Sussex John Wiley & Sons Inc , 2015
Buku Teks SO
Unrau, Harlan D.
National Park Service, 1976
Buku Teks SO