Lord, Peter, author
E&FN Spon, 1996
Buku Referensi
Artikel Jurnal
Hutahaean, Ramses Y., author
Andi, 2012
Buku Teks
Graham, Benjamin, 1894-1976, author
McGraw-Hill, 1962
Buku Teks
Lee W. Graber, Robert L. Vanarsdall, Katherine W.L., editor
Elsevier Mosby, 2012
Buku Teks