Turner, Bryan S., author
Sage, 1983
Buku Teks
Bouquet, A.C., author
Penguin Books, 1953
Buku Teks
Stein, Rebecca L., author
Pearson Education, 2005
Buku Teks
Council for Research in Values and Philosophie, 2004
Buku Teks
Thompson, Ian
Longman, 1965
Buku Teks