Answer: Here's a link or two!
https://www.nature.com/subjects/classical-conditioning#research-and-reviews
https://www.ncbi.nlm.nih.gov/books/NBK470326/
(FYI: For the second link, there is also a little arrow that's pointing downwards. It is located on the far top right side of each new section in the article. If you click on that you will see some extra links/stuff that may help you gain more info.
Oh! Also, down to the paragraph where it says "Issue of Concern" is a good little section to read. Hope this helps <3)
