Easton, Stewart C., author
Praeger, 1964
Buku Teks
Nicoll, Allardyce, author
George G. Harrap, 1949
Buku Teks
edited, Daniel D. Mcgarry, Clarence L. Hohl
Houghton Miffiln, 1963
Buku Teks
Bingham, Woodbridge, author
Waverly Press, 1941
Buku Teks
Kopp, Hermann, author
Springer, 2012
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