Theodorson, George A., author
Barnes & Noble Books, 1969
Buku Referensi
edited by Henry Praty Fairchild
Littlefield, Adams & Co., 1962
Buku Referensi
Jary, David
Harper Collins, 1991
Buku Teks
Robertson, David, author
Europa Publications Limited, 1987
Buku Referensi
Donald, Graeme, author
Simon & Schuster, 1994
Buku Referensi