Horowitz, Anthony, 1955-, author
Victoria Bolinda Audio, 2013
Buku Teks
Potapova, Nina F., author
Progress Publishers, [196-]
Buku Teks
Katzner, Kenneth, author
John Wiley & Sons, 1994
Buku Referensi
Doob, Leonard William, 1909-, author
The Cresset Press, 1948
Buku Teks
Gallup, George
Princeton University press, 1948
Buku Teks