Vega Michel, C., M. López Álvarez, and E. Camacho Gutiérrez. “Behavioral Patterns in Avoidance Schedules With Humans and Their Effects on Salivary Cortisol”. Mexican Journal of Behavior Analysis, vol. 36, no. 1, May 2010, pp. 33-46, doi:10.5514/rmac.v36.i1.18013.