Free Pr, 1959
Buku Teks
University of London Institute of Education, 1979
Buku Teks
edited by L. Andries van der Ark
Lawrence Erlbaum Associates, 2005
Buku Teks
Lasswell, Harold D.
Routledge & Kegan Paul, 1952
Buku Teks
Pirie, Madsen, 1940-
Wildwood House, 1988
Buku Teks