Williams, D. A., Mehta, R., Poworoznyk, T. M., Orihel, J. S., George, D. N., & Pearce, J. M. (2002). Acquisition of superexcitatory properties by an irrelevant background stimulus. Journal of Experimental Psychology: Animal Behavior Processes, 28(3), 284-297. https://doi.org/10.1037//0097-7403.28.3.284