Bohler, Jochen, author
Oxford University Press, 2017
eBooks
Robinson, O.F., author
Frofessional Books Limited, 1985
Buku Teks
Benns, Lee F., author
Appleton-Century-Crofts, 1955
Buku Teks
edited by John A. Wolter and Ronald E. Grim
Library of Congress, 1977
Buku Referensi
Weber, Alfred, 1868-1958, author
Kegan Paul, 1947
Buku Teks