Mulvaney, Robert J., author
Essex Pearson, 2014
Buku Teks
editor, James A. Gould
Charles E. Merrill , 1971
Buku Teks
Pojman, Louis P., author
Thomson Wadsworth, 2006
Buku Teks
Cornman, James W., author
Macmillan, 1968
Buku Teks
Hospers, John, author
Roudledge, 1988
Buku Teks