Poole, Ernest
Nancy Flyer; a stagecoach epic
New York, Thomas Y.Creweel, 1949
 Buku Teks
Roy, Gabrielle
Hidden mountain
McClelland and Steward, 1975
 Koleksi Publik
Capra, Fritjof
The hidden connections
HarperCollins, 2002
 Buku Teks
Cole, John W.
The Hidden frontier
Academic Press, 1974
 Buku Teks SO
Packard, Vance
The hidden persuaders
Penguin, 1960
 Buku Teks SO