Budi Marwoto
Kementerian Pertanian RI, 2013
Artikel Jurnal
Wojciechowski, Jerzy A.
Council for research in values and philosophy, [Date of publication not identified]
Buku Teks SO
Odum, Eugene Pleasants
Saunders College, 1983
Buku Teks
Pianka, Eric R.
Harper & Row, 1988
Buku Teks
Dash, Madhab C.
Tata McGraw-Hill , 2003
Buku Teks