Put this on another forum if appropriate but I have mostly QM in mind. Is there an online source for classical papers, and in particular for obviously desirable translations of classical papers, which in QM were often in German? If with historical or scholarly gloss giving additional perspective, so much the better. My reason for asking is that IMHO textbooks often skimp certain things. There was once advice ‘study the masters, not their pupils’. For instance you are often told very summarily that the wavefunction ψ is to be interpreted as ψ squared is proportional to probability density. Rather like an engineering formula ‘use this, it always gives the right answer’. One would like to know how the originators (Born?) convinced themselves and others of it. I find symmetry and antisymmetry of wavefunctions for 2 particles treated rather the same way, but may make a separate post about that. Another way I find the textbooks defective is their insincere lipservice to the overriding importance of experiment. It looks as though since the mathematical treatments are such a barrier, books confine themselves to that after which they quickly croak out ‘and this result agrees with experiment’ and race on to the next math treatment. So access to the experimental publications would be useful too.