Hyde, William De Witt, author
Macmillan, 1959
Buku Teks
Stumpf, Samuel Enoch, 1918- 1998, author
McGraw-Hill, 1999
Buku Teks
edited by Vergilius Ferm
Littlefield, Adams & Co., 1961
Buku Teks
Stumpf, Samuel Enoch, 1918-1998, author
McGraw-Hill, 1989
Buku Teks
Windelband, Wilhelm, author
Dover, 1956
Buku Teks