Cognitive Processes Associated with Sequential Tool Use in New Caledonian Crows Wimpenny, Joanna H. ; Weir, Alex A. S. ; Clayton, Lisa ; Rutz, Christian ; Kacelnik, Alex Abstract Publication: PLoS ONE Pub Date: August 2009 DOI: 10.1371/journal.pone.0006471 Bibcode: 2009PLoSO...4.6471W