Two appear to be freely available for download from the Internet Archive. https://archive.org/details/DemidovichEtAlProblemsInMathematicalAnalysisMir1970 https

Two appear to be freely available for download from the Internet Archive. https://archive.org/details/DemidovichEtAlProblemsInMathematicalAnalysisMir1970 https://archive.org/details/DemidovichEtAlProblemsInMathemat... https://archive.org/details/n.-piskunov-differential-and-integral-calculus-mir-1969 https://archive.org/details/n.-piskunov-differential-and-int... Another has at least some of the volumes available to borrow from IA. https://archive.org/details/courseofhigherma0005smir https://archive.org/details/courseofhigherma0005smir And of course there's always Ebay, Alibris, Bookfinder, etc. Or the various pirate e-book sites if one is interested in that sort of thing.