Eucken Walter
William Hoodge and Co, 1950
Buku Teks
Berrie, T. W. (Tom W.)
Peter Peregrinus, 1992
Buku Teks
Weber, Max, 1864-1920, author
New York,N.Y. Free Press 1964,
Buku Teks
Meier, Gerald M., author
Wiley, 1966
Buku Teks
Bade, Robin, author
Pearson, 2013
Buku Teks