Akins, C., Klein, E., & Zentall, T. (2002). Imitative learning in Japanese quail (Coturnix japonica) using the bidirectional control procedure. Animal Learning & Behavior, 30(3), 275-81. https://doi.org/10.3758/bf03192836

Klein, E., Gehrke, B., Green, T., Zentall, T., & Bardo, M. (2007). Repeated cocaine experience facilitates sucrose-reinforced operant responding in enriched and isolated rats. Learning and Motivation, 38(1), 44-55. https://doi.org/10.1016/j.lmot.2006.07.004

Stairs, D., Klein, E., & Bardo, M. (2006). Effects of environmental enrichment on extinction and reinstatement of amphetamine self-administration and sucrose-maintained responding. Behavioural Pharmacology, 17(7), 597-604. https://doi.org/10.1097/01.fbp.0000236271.72300.0e

Klein, E., Gehrke, B., Green, T., Zentall, T., & Bardo, M. (2007). Repeated Cocaine Experience Facilitates Sucrose-Reinforced Operant Responding in Enriched and Isolated Rats. Learning and Motivation, 38(1). https://doi.org/10.1016/j.lmot.2006.07.004