>>11276565Example, I work with p-adic groups. My advisor started out in that area and worked out in great detail: Borel’s book on algebraic groups, Satake’s book on the classification of reductive groups over non algebraically closed fields, Humphreys and Bourbaki’s books on Lie algebras, Macdonalds’ book on p-adic integration, parts of Bruhat-Tits and a few other foundational articles.
But there are plenty of books/articles related to representation theory, harmonic analysis, symmetric spaces, local fields, topological groups or group schemes that he did not read in detail because he has never had a use for that, but with the content of which he is familiar enough to refer me to them if needed.