For the Polish pact: https://en.wikipedia.org/wiki/German%E2%80%93Polish_Non-Aggr...

Here: https://www.youtube.com/watch?v=pJwoygYdTmY is an exchange between Tusk and Putin on the topic. I haven't found a better video.

About the Molotov negotiation, it is in the book by Nikolai Starikov, Who set Hitler against Stalin?, (ISBN 978-5-496-00332-2). It is in Russian, unfortunately. Excerpts have been translated to English, the part I was talking about is here: https://orientalreview.org/2015/04/18/episode-15-poland-betr...