Complex sentence: Probably his most influential publication was in 1959 which helped to set behavior modification in motion leading to the establishment of the discipline of applied behavior analysis and the Journal of Applied Behavior Analysis (JABA).
Split into simpler sentences: Probably his most influential publication was in 1959 which helped to set behavior modification in motion. This, in turn, lead to the establishment of the discipline of applied behavior analysis and the Journal of Applied Behavior Analysis (JABA).