Johnson, Falk S., author
Houghton Mifflin, 1965
Buku Teks
Sharples, Mike, 1952-, author
Routledge, 1999
Buku Teks
Jolly, David, author
Cambridge University Press, 1984
Buku Teks
Behrman, Carol H., author
Applied Research in Education, 2000
Buku Teks
Riebel, John P., author
Arco, 1978
Buku Teks