Artikel Jurnal
Anderson, Francis M.
Ransdell Incorporated Publishers, 1939
Buku Teks
edited by George W. Keeton and Georg Schwarzenberger
Stevens and Sons, 1967
Buku Teks SO
Holmes, Oliver Wendell
Little, Brown, 1923
Buku Teks
Holmes, Oliver Wendell
Little, Brown, 1963
Buku Teks