The Black Book of Polish Censorship (Czarna ksiega cenzury PRL) consists of approximately 700 pages of classified documents, which the Cracow censor, Tomasz Strzyzewski, smuggled out of People's Poland to Sweden in February 1977.
arts.gla.ac.uk/Slavonic/staff/Blackbook.html
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library.cornell.edu/colldev/slav/publishinghistory.html
A Brief History of Polish Underground Publishing During Solidarity
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(History of Poland 1914-1939), was printed posthumously. Due to the government crackdown on opposition the book was heavily censored....
the Polish communist censorship completely removed any mention of the Molotov-Ribbentrop Pact (Nazi Germany-Soviet alliance) and the section on the Soviet invasion of Poland on 17 September 1939 together with the photo of the German-Soviet parade in Brześć was removed and replaced with a general note on changed borders.
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Polish cinema got around censorship sometimes and was at it's height, in my opinion, during the communist regime.
It is an amazing ability of man to be so creative when persecuted or the great quote is "After all it's not that awful. Like the fella says, in Italy for 30 years under the Borgias they had warfare, terror, murder, and bloodshed, but they produced Michelangelo, Leonardo da Vinci, and the Renaissance. In Switzerland they had brotherly love - they had 500 years of democracy and peace, and what did that produce? The cuckoo clock"
I suggest watching these but they are all in Polish, they use metaphors for communism or just laugh at it directly: Alternatywy Cztery (in Polish), Kingsajz, Rozmowy kontrolowane, Mis, Seksmisja.