Journal Article
Auersperg, A. M. I.; van Horik, J. O.; Bugnyar, T.; Kacelnik, A.; Emery, N. J.; von Bayern, A. M. P.: Combinatory actions during object play in Psittaciformes (Diopsittaca nobilis, Pionites melanocephala, Cacatua goffini) and Corvids (Corvus corax, C. monedula, C. moneduloides). Journal of Comparative Psychology
129 (1), pp. 62 - 71 (2015)