Koons, Robert C, author
Wiley Blackwell, 2017
Buku Teks
edited by Jaegwon Kim
Blackwell Publishing, 1999
Buku Teks
Pepper, Stephen C.
University of California Press, 1966
Buku Teks
Vaske, Martin O.
McGraw-Hill, 1963
Buku Teks
Loux, Michael J., author
Routledge, 2002
Buku Teks