Roland, Charles P.
McGraw-Hill, 1991
Buku Teks
by Thomas L. Hartshorne ... [and others]
Longman, 2003
Buku Teks
Phillips, Christopher, author
Oxford University Press, 2016
eBooks
Hansen, Harry, author
A Mentor Book, 1961
Buku Teks
Caravan, Jill, author
Todtri Production Limited, 1996
Buku Referensi