McIntosh, Jane
The practical archaelogist: how we know what we know about the past
Checkmark Books, 1999
 Buku Referensi
Cochrane, Susan H.
Fertility and education: what do we really know?
Johns Hopkins University Press, 1979
 Buku Teks SO
Rabe, Cynthia Barton
The innovation killer: how what we know limits what we can imagine-- and what smart companies are doing about it
American Management Association, 2006
 eBooks
What do products/services cost how do we know?
 Artikel Jurnal
Overstreet, Harry
What we must know about communism / by Harry and Bonaro Overstreet
W.W. Norton, 1958
 Buku Teks SO