I'm writing a paper which involves a lot of quantum mechanics. As a result of this, I'm finding it necessary to cite the likes of Einstein, Born and Jordan.

Particularly in the case of Einstein, due to the amount of times he has been quoted online and the fact that most of his original works were in private letters or German journals, I'm struggling to find the original source for some of his quotations.

Specifically, I want to quote:

We must use sometimes the one theory and sometimes the other, while at times we may use either.

with reference to wave-particle duality. It's a pretty well established translation of a quotation of Einstein, however, I've been unable to find the original source of this in over an hour of searching.

  • 3
    $\begingroup$ Have you searched the book "Albert Einstein, Leopold Infeld (1938). The Evolution of Physics"? I found the reference in the wiki page Wave–particle duality $\endgroup$
    – Nobody
    Nov 29, 2019 at 13:51
  • $\begingroup$ @scaaahu I had not, thank you. I feel my question still has utility as a more general case of what one should do when the exact origin of a well known quotation cannot be found though so I'll leave it open $\endgroup$
    – Persistence
    Nov 29, 2019 at 13:57
  • $\begingroup$ Visit Open Library. Many gems there. openlibrary.org/… $\endgroup$
    – Rita Geraghty
    Nov 30, 2019 at 6:44

1 Answer 1


You can find it on Einstein’s Google citations

You can then use Google Translate.

  • $\begingroup$ Thanks, that google scholar user page thing will prove very helpful $\endgroup$
    – Persistence
    Nov 29, 2019 at 16:56
  • $\begingroup$ @Persistence In google schoolar top left you can access statistics. Also, when you click on an article , under it there an option of 'cited by', that one leads you to a list of materials that cited the article you are checking. Good luck. $\endgroup$
    – deags
    Nov 29, 2019 at 19:09

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