Hyman, David N., author
Holt, Rinehart and Winston, 1973
Buku Teks
edited by Herbert C. Morton
Brookings Institution, 1965
Buku Teks
Silberling, Norman J., author
McGraw-Hill, 1943
Buku Teks
Charlesworth, James C. (James Clyde), 1900-, author
Harper, 1951
Buku Teks
Mikesell, R.M., author
Richard D. Irwin, 1961
Buku Teks