Elder, Neil C.M.
Pergamon Press , 1970
Buku Teks
Lindstrom, Eric
Swedish Institute, 1982
Buku Teks
University of Minneapolis Press, 1975
Buku Teks
Arneson, Ben Albert,1883-1958.
D. Van Nostrand, 1949.
Buku Teks
Copeland, Melvin T., author
Harvard University Press, 1955
Buku Teks