Osborn, Richards C.
Harper & Brothers, 1959
Buku Teks
Hamilton, Robert W.
St. Paul, Minn, 1989
Buku Teks
Husband, William H., author
Richard D. Irwin, 1948, 1955, 1962
Buku Teks
Masson, Robert L., author
McGraw-Hill, 1935
Buku Teks
Burtchett, Floyd Franklin
Clifford Milton, 1964
Buku Teks