Pojman, Louis P., author
New York : Oxford University Press, 2000
Buku Teks
Macmillan, 1971
Buku Teks
Park, Michael Alan, author
Mayfield , 1998
Buku Teks
Park, Michael Alan, author
Mayfield , 2000
Buku Teks
Darwin, Charles Robert
New York Henry Schuman 1950
Buku Teks