Pott, F.L. Hawks, author
Kelly and Walsh, 1936
Buku Teks
Smedley, Agnes, author
Vanguard Press, 1933
Buku Teks
Chu, Charles C.J.
Buku Teks
Hoffding, Harold, author
Macmillan, 1955
Buku Teks
Brandt, Conrad, author
George Allen and Unwin, 1959
Buku Teks