Gregory, Derek, author
McGraw-Hill , 1978
Buku Teks
Tippet, L.H.C.
Oxford University Press, 1950
Buku Teks
Fleming, Michael C., author
Prentice-Hall, 1991
Buku Teks
Guilford, J. P. (Joy Paul), 1897-1987, author
McGraw-Hill , 1978
Buku Teks
Hogg, Robert V., author
Macmillan, 1969
Buku Teks