> Is it possible that the articles really were not available, as they used the data from sep-2015 to feb-2016, early version of SciHub? That's within the realm

> Is it possible that the articles really were not available, as they used the data from sep-2015 to feb-2016, early version of SciHub? That's within the realm of possibilities but sure doesn't sound like the case the way they described their methodology. That would have required a catalog of available papers on Sci-Hub too, but the dataset they used only contained download logs, so they couldn't have known whether a zero-download paper was available or not (unless I misunderstood what the first dataset is about).