Books/articles/journals/reports/essays are the main source whatever you are interested in or working on.
Remember that :
“BOOKS ARE OUR BEST FRIENDS, EVEN THOUGH THEY TURN THEIR BACK TO US ! “
My own library are the best source I have at my disposal for all my activities, and over the years I have assembled thousands of books and reprints, which makes me rather independent of external libraries.
I have sections with : mineralogy, mycology, philosophy, botany, philately, numismatic, natural sciences, encyclopedia, gastronomy, general literature and fiction…., as well as specialities on Madame Curie and her relatives, philosopher Arne Næss, explorer Thor Heyerdahl, martial arts, Taoism, Zen-buddhism, psycology, ...............