Kennish, Michael J., author
CRC Press, 1991
Buku Teks
Wojciechowski, Jerzy A., author
Council for research in values and philosophy, [Date of publication not identified]
Buku Teks SO
Odum, Eugene Pleasants, author
Saunders College, 1983
Buku Teks
Pianka, Eric R., author
Harper & Row, 1988
Buku Teks
Dash, Madhab C., author
Tata McGraw-Hill , 2003
Buku Teks