Artikel Jurnal
Labarge, Margaret Wade
Beason Press, 1986
Buku Teks SO
edited by John A. Kromkowski, Robert R. Magliola and George F. McLean
Council for Research in Values and Philosophie, 2004
Buku Teks SO
Nadiesyah Hosen, Richard Mohr, editor
Routledge, 2011
Buku Teks
Korean Overseas Information Service, 1978
Buku Teks SO