Osborne, George Edward, author
West Publishing, 1951
Buku Referensi
Walsh, William F. (William Francis), 1875-1946, author
Callaghan, 1934
Buku Teks
Warr, George, author
Sweet & Maxwell, 1994
Buku Teks
Hales, Michael G.
Prentice-Hall, 198
Buku Teks
Prosser, William L., author
West Publishing, 1971
Buku Teks