Doichev, R. L. (?????.).  (1973).  [A study on the migration of the starling (Sturnus vulgaris L.) in Bulgaria] (in Bulg). Godishnik na Sofiiskiya Universitet. Biologisheski Fakultet. Kniga I. Zoologiya, Fiziologiya i Biokimiya na Zhivotnite, 65, 11-21.