Dawn, Hawkins
Oxford University Press, 2009
Buku Teks
McKillup, Steve, author
Cambridge University Press, 2011
Buku Teks
Milton, Janet Susan, author
McGraw-Hill, 1983
Buku Teks
Milton, Janet Susan, author
McGraw-Hill , 1992
Buku Teks
Creswell, John W., author
Sage, 1994
Buku Teks