edited by Vergilius Ferm
Littlefield, Adams & Co., 1961
Buku Teks
Stumpf, Samuel Enoch, 1918-1998
McGraw-Hill, 1999
Buku Teks
Stumpf, Samuel Enoch, 1918-1998
McGraw-Hill, 1989
Buku Teks
Windelband, Wilhelm
Dover, 1956
Buku Teks
Cassey, Edward S
The university of California press, 1997
Buku Teks