American Association for the Advancement of Science, 2018
Majalah, Jurnal, Buletin
Geoff Green, Ken Petford, Alan Short, David Walker
John Muray, 1975
Buku Referensi
Tillery, Bill W.
McGraw-Hill, 2013
Buku Teks SO
Butterfield, Herbert
The Free Press , 1957
Buku Teks SO
Ramsey, William L.
Holt, Rinehart and Winston, 1961
Buku Teks