[1]
Ardamatskaya, T.B. and Korzyukov, A.I. 2013. Numbers and distribution of Mute Swans Cygnus olor Whooper Swans C. cygnus and Bewick’s Swans C. bewickii in the Black Sea area of the Ukraine, USSR. Wildfowl. (Apr. 2013), 53–55.