Arnold, David, author
Routledge, 1994
Buku Teks
Herrmann, Paul
Harper & Brothers , 1956
Buku Teks
Goetzmann, William H.
Viking, 1986
Buku Teks
Stammler, Wolfgang
Stuttgart JB Metztersche 1950
Buku Teks
Boase, Alan
University Paperbacks, 1964
Buku Teks