Hunt, Kellogg W., author
Houghton Miffiln, 1967
Buku Teks
Potter, Simeon, author
Penguin Books, 1979
Buku Teks
Ballard, Robert D., author
National Geographic Society, 1983
Buku Referensi
edited by Claude T. Bissell
Published in association with Carleton University by University of Toronto Pres, 1957
Buku Teks
edited by Robert L. McDougal
University of Toronto Press in association with Carleton University, 1959
Buku Teks