Bartels, Robert
Richard D. Irwin, 1962
Buku Teks SO
United Nations Bureau of Social Affairs , 1955
Buku Teks SO
Matherson, Ross
John Wiley & Sons, 1978
Buku Teks SO
Paley, Morton D.
Clarendon Press, 1970
Buku Teks SO
Chang, Carsun
Bookman Associates, 1962
Buku Teks SO