Clarke, Keith C.
Prentice-Hall, 1999
Buku Teks
Artikel Jurnal
Iwan Gunawan, Lena Sumargana, Nani Hendiarti, Guy Adamsyah
Directorate of technology for natural resources development, 1995
Buku Referensi
Johnson, Lynn E., author
CRC Press, Taylor & Francis Group, 2009
Buku Teks
Wadsworth, Richard
Longman limited , 1999
Buku Teks