McColvin, Eric
Longmans, Green and Co., 1946
Buku Teks
Gluck, Peter L.
Rockport Publishers, 1997
Buku Teks
Marcucci, Luisa
Studio Books , 1960
Buku Referensi
O`Sullivan, Jeremiah Francis, 1903-
Appleton Century Croffs, 1943
Buku Teks
Hoffman, Ross J.S.
Littlefield, Adams, 1958
Buku Teks