Please specify if terms of license are complied with!Jean Brainard (April 14, 2009). "Animal Behavior". CK-12 Flexbooks.
Re-used at http://www.heise.de/tp/artikel/38/38724/1.html
Please specify if terms of license are complied with!Peter Mühlbauer (11-03-2013). "Schmerzhafter Tierschutz". Telepolis.