Engler, Calvin, author
Irwin, 1989
Buku Teks
edited by Georg Heeg ... [and others]
Prentice-Hall, 1992
Buku Referensi
Huffman, Franklin E.
Yale University Press, 1986
Buku Referensi
The Australian National University, 1982
Buku Teks
Staples, Frederick
The Counting House Publishing , 1938
Buku Teks