(1)
Pulliainen, E.; Helle, P.; Tunkkari, P. Adaptive Radiation of the Digestive System, Heart and Wings of Turdus Pilaris, Bombycilla Garrulus, Sturnus Vulgaris, Pyrrhula Pyrrhula, Pinicola Enucleator and Loxia Pytyopsittacus. Ornis Fenn 1981, 58, 21–28.