Buku Teks
Elliott, William Y., author
Prentice-Hall, 1950
Buku Teks
Easton, Stewart C., author
Holt, Rinehart and Winston, 1966
Buku Teks
edited by John Louis Beatty, Oliver A. Johnson
Prentice-Hall, 1966
Buku Teks
McDonald, Lee Cameron, author
Harcour Brace Jovanwich, 1968
Buku Teks