Manila: National Library of Philippine, 1978 - 1984
Buku Referensi
Artikel Jurnal
edited by Daniel B. Botkin [and others]
Academic Press, 1989
Buku Teks
Monsen, Joseph R.
McGraw-Hill, 1973
Buku Teks
Starling, Grover, author
Kent Publishing Company, 1984
Buku Teks