Flesch, Rudolf
Harper & Brothers, 1958
Buku Teks
Wilson, George P., author
F.S. Crofts, 1947
Buku Teks
Yates, Paulene M.
Harper & Row, 1962
Buku Teks
London Collier-Macmillan 1965,
Buku Teks
Hubbard, L. Ron, 1911-1986, author
L. Ron Hubbard Library, 2009
Multimedia