3 incredibly useful books. Even with the internet, these will be used by any serious student. They also contain answers to the hard-to-find problems professors assign if you know where to look. Even with a little age on them, they are still highly relevant. Most of this material hasn’t changed in a hundred years. The Chemical dictionary is copyright 1961. The Physics Handbook was legally acquired from a career center.  I worked there. The copyright is 1967. The gorgeous Handbook of Chemistry and Physics is dated 1979. Weight is 18 pounds. Media mail is 16.82. Sip to US only.