What are the key dates for the development of operant conditioning?
It would have been pretty strange for there to be multi-year gaps in Skinner's publication record, and in fact, Skinner continued to publish every year in both of those periods and beyond (Epstein, 1977). I've provided a link to a list of his publications which includes both periods, but there is no real way to say which of these publications were the 'key' studies for operant conditioning. Hopefully, this will still be of some help.

References


Epstein, R. (1977). A listing of the published works of BF Skinner, with notes and comments. Behaviorism, 99-110.