American Association for the Advancement of Science, 2018
Majalah, Jurnal, Buletin
Ridley, B.K., author
Routledge, 2001
Buku Teks
Hoffmann, Stanley
N.Y. Praeger , 1965
Buku Teks
Bennett, Christine I.
Allyn and Bacon , 1986
Buku Teks
F.E. Peacock Publishers, Ind., 1972
Buku Teks