*[http://www.custance.org/Library/Volume4/Part_I/chapter6.html Nilsson, Heribert, Synthetische Artbildung, Verlag CWK Gleerup, Lund, Sweden, 1953, page 1185 | *[http://www.custance.org/Library/Volume4/Part_I/chapter6.html Nilsson, Heribert, Synthetische Artbildung, Verlag CWK Gleerup, Lund, Sweden, 1953, page 1185 |