Goller F , Riede T. Integrative physiology of fundamental frequency control in birds . J physiol Paris.
Volodin IA . Behavior repertoire of Rufibrenta ruficollis.2. Acoustic behavior . zool zh.1990b;69(10):98-106.
W.Astuti , A.M , Aibinu,M.J.E Salami , R.Akmelawati , And Asan G.A Muthalif , Managimg Animals sounds – Some challenges And Research Directions ,2009.Fern , Audio Classification of Bird species : a Statistical Manifold Approach . Corvallis.