Graham, John, author
Penguin Books, 1983
Buku Referensi
Young, E.C., author
Penguin Books, 1988
Buku Referensi
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