Hitchcock, Terrance S.
Dow Jones-Irwin, 1982
Buku Teks SO
Robertson, Ross M.
Harcourt, Brace & World, 1964
Buku Teks
edited by Harold F. Williamson
Prentice-Hall, 1951
Buku Teks
Davies, J. Kenneth, 1925-
J.B. Lippincott, 1970
Buku Teks SO
Krooss, Herman Edward, 1912-1975
Prentice-Hall, 1955
Buku Teks SO