Hornby, Albert Sydney, author
Oxford University Press, 1954
Buku Referensi
Graver, B.D.
Oxford University Press, 1990
Buku Teks
Spiegel, Murray R., author
McGraw-Hill, 1988
Buku Teks
Folomkina, S., author
Moscow State Publishing House
Buku Referensi
Eysenck, Michael W., author
Psychology Press, 2001
Buku Referensi