“Finding something is easy: it’s knowing that you ought to have looked for it that is hard. You search for known items only once you have done all the real work. In the really important cases, you search for known items only once you already know what they are going to say. In short, if we knew ahead of time what the questions were and what books probably answered them, there would be no reason to do the research.”
Andrew Abbott, 2014, Digital Paper: A Manual for Research and Writing with Library and Internet Materials.