Artikel Jurnal
Fitri Prawitasari
Fakultas Ilmu Pengetahuan Budaya Universitas Indonesia, 2012
UI - Skripsi Open
Grossman, 1967
Buku Teks
Hughes-Hassell, Sandra
[American Library association, American Library association], 2005
eBooks
New York National Bureau of Economic Research, 1947 c.1943,
Buku Teks