Anglin, W.S.
Springer-Verlag, 1994
Buku Teks
Burton, David M.
McGraw-HIl, 1996
Buku Teks
edited by Astrik L. Gabriel
Mediaeval Institute, University of Notre Dame, 1974
Buku Teks
Bergamini, David, author
Time Incorporated, 1963
Buku Referensi
Hemming, 1998
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