Hubbard, L. Ron, 1911-1986, author
Hermitage House, 1950
Buku Referensi
Alison Butterworth
Blurb, 2018
Buku Teks
Lykknes, Annette, editor
Springer, 2012
eBooks
John Wiley & Sons, 1992
Buku Teks
Jelveus, Anders, author
Elsevier Churchill Livingstone, 2011
Buku Teks