Well, the scenes in which Ikaria crew find remains of "capitalist" ship from XXth century are taken directly from Nebula. Although I'm sure this particular motive is one of the things Lem was least proud of. It's easy to find on youtube, it's the only fragment I have seen so far. Quite interesting, nice classic feeling. Being from Poland myself (and having lived some under communism) I find the depiction of the capitalists very familiar:)