Lens, Willy, Maria Paula Paixão, e Dora Herrera. «Instrumental Motivation Is Extrinsic Motivation: So What???». Psychologica0, no. 50 (Janeiro 1, 2009): p. 21-40. Acedido Junho 4, 2025. https://impactum-journals.uc.pt/psychologica/article/view/1647-8606_50_2.