AFAIK it is taught in Soviet military academies since 1960s being a common knowledge there. Maybe it’s part of Khruschev antistalinist propaganda but there are a lot of facts behind this.
There are Western studies as well:
Pariahs, Partners, Predators: German-Soviet Relations, 1922-1941
http://findarticles.com/p/articles/mi_qa3686/is_3_33/ai_n28721777/
Soviet-German relations before 1941
Information about Soviet-German relations before 1941
http://english.turkcebilgi.com/Soviet-German+relations+before+1941
I ‘ve just find it from yahoo right now. You can make deeper research if you want it.
Thank you for linking it and its correct. No further research is necessary.