Edwards, Corwin D.
Press of Western Reserve University, 1956
Buku Teks
Warner, W. Lloyd
Harper & Brothers , 1955
Buku Teks
Kaplan, A.D.H.
Brookings Institutions, 1959
Buku Teks
Hidy, Ralph W
Haper, 1955
Buku Teks
Sitompul, Luhut Gravelino Daud Hotman
2003
UI - Tesis Membership