Dávila de León, María Celeste and Fernando Chacón Fuertes. “Prediction of Longevity of Volunteer Service: A Basic Alternative Proposal”. The Spanish Journal of Psychology, vol. 10, vol. 10, no. 1, 2007, pp. 115-21, https://revistas.ucm.es/index.php/SJOP/article/view/SJOP0707120115A.