Vinogradov, V G, and E M Auezov. 2013. “Numbers, Distribution and Breeding Success of Whooper Swans Cygnus Cygnus and Mute Swans C. Olor in Central Kazakhstan, USSR, in 1985 and 1987”. Wildfowl, April, 73-76. https://tidsskrift.dk/Wildfowl/article/view/154998.