Goldwater, Rober
Murray, 1976.
Buku Teks
Schwarz, Karl, author
Philosophical Library, 1949
Buku Teks
Longman, 1998
Buku Teks
Carlson, Paul A., author
South Western, 1957
Buku Teks
edited by E.M. Kirkpatrick ; assistant editors, C.M. Schwarz ... [and others]
Chambers, 1983
Buku Referensi