edited by P. Edward Haley, David M. Keithly, and Jack Merritt
Westview Press, 1985
Buku Teks
Robin, Ranger
Gage, 1979
Buku Teks
Edward, David V.
Holt, Rinehart and Winston, 1969
Buku Teks
edited by Wolfram F. Hanrieder
Westview Press, 1986
Buku Teks
Prentice-Hall, 1964
Buku Teks