c. 1987
Buku Referensi
Borland International, 1988
Buku Referensi
Lewis, Norman, author
Harper & Row , 1962
Buku Referensi
edited by Tyler G. Hicks
McGraw-Hill, 1986
Buku Referensi
editor, David Hollis
British Museum (Natural History), 1980
Buku Referensi