Artikel Jurnal
Maasdorp, A.F.S., Sir
Juta & Co., 1948
Buku Teks
Marcucci, Luisa, author
Studio Books , 1960
Buku Referensi
O`Sullivan, Jeremiah Francis, 1903-, author
Appleton Century Croffs, 1943
Buku Teks
Hoffman, Ross J.S., author
Littlefield, Adams, 1958
Buku Teks