Lendrum, Tony
McGraw-Hill, 1995
Buku Referensi
Greenwood, Ronald G.
Lexinton Books, 1974
Buku Teks
Ali Masykur Musa
Lembaga Pangkajian MPR RI, 2017
Artikel Jurnal
Raymond, Thomas Cicchino
McGraw-Hill, 1964
Buku Teks
Raymond, Thomas Cicchino
McGraw-Hill, 1955
Buku Teks