Osborn, Richards C.
Harper & Brothers, 1959
Buku Teks SO
Hamilton, Robert W.
St. Paul, Minn, 1989
Buku Teks
Hamilton, Robert W.
West Publishing, 1984
Buku Teks SO
Husband, William H.
Richard D. Irwin, 1948, 1955, 1962
Buku Teks SO
Masson, Robert L.
McGraw-Hill, 1935
Buku Teks SO