Johansen, Bob
Berrett-Koehler, 2012
Buku Teks
LeBlanc, Robin M.
University of California Press, 1999
Buku Teks SO
foreword by Emrys Jones
Octopus Books, 1978
Buku Referensi
edited by Gerald W. Whitted
Pan American World Airways, 1971
Buku Referensi
Huxley, Aldous, 1894-1963
Vintage Publishing, 2018
Buku Teks SO