edited by Robert Finch and John Elder
W.W. Norton, 2002
Buku Teks
Quammen, David
Schocken Books , 1985
Buku Teks
Yates, Steve, author
Facts On File, 1992
Buku Referensi
MacKinnon, Kathy, author
Gramedia Pustaka Utama, 1992
Buku Teks
selected and edited by Alec H. Chisholm
Angus & Robertson, 1964
Buku Teks SO