Avian cognition and social interaction: Fifty years of advances

2011

Cognitive and communicative abilities of grey parrots

2006

Cognitive and communicative capacities of grey parrots — implications for the enrichment of many species

2004

In search of King Solomon's ring: Cognitive and communicative studies of grey parrots (Psittacus erithacus)

2001

Rethinking syntax: A commentary on E. Kako's "Elements of syntax in the systems of three language-trained animals"

1999