Goodall, Brian, author
Penguin Books, 1987
Buku Referensi
edited by Valerie H. Pitt
Penguin Books, 1991
Buku Referensi
E.C. Young
Allen Lane, 1979
Buku Referensi
Peter, author
Penguin, 1978
Buku Referensi
Bannock, G., author
Penguin Books, 1974
Buku Referensi