A. C. S. Santos, B. G. de A. Ribeiro, J. T. Martins, M. J. Q. Galdino, M. L. do C. C. Robazzi, and R. P. Ribeiro, “Motivations of retired professors to return to work activities at a public university”, Rev Rene, vol. 17, no. 4, pp. 561–568, Aug. 2016.