Panjaitan, Ostina E., author
Yayasan Sumber Agung, 1997
Buku Teks
Fritzman, J. M., author
Polity Press , 2014
Buku Teks
Cairns, Huntington, 1904-1985, author
Johns Hopkins Press, 1967
Buku Teks
Cairns, Huntington, author
The John Hopkins Press, 1949
Buku Teks
Stace, W. T.
Dover Publications, Inc., 1923
Buku Teks