The borrowing registers of university libraries represent ‒ especially for the history of science ‒ a new source genre and thus a new approach. They enable to reconstruct the decisive influences and stimuli on scientists working at the places in question. In this article, this is exemplified by the Göttingen mathematician Bernhard Riemann (1826–1866), who, apart from a few stays abroad, lived and worked almost exclusively in Göttingen. In the first section, the Göttingen University Library borrowing registers are introduced and the most important previous book-historical publications related to them are presented. In the second section, I first describe how and why I came to examine these registers with reference to Riemann, and present in the following some new results regarding the genesis of Riemann’s groundbreaking philosophical as well as mathematical ideas. I conclude with an unaltered photomechanical reproduction of Riemann’s book and journal borrowings from the Göttingen University Library, as I extracted and compiled them quite some time ago without the use of digital tools. The definitive edition of this article will be published in an appropriate journal for the history of science after having been revised and then translated into English in post-Covid times, with further consultation of the originals in Göttingen. For the convenience of English-speaking readers, a work-in-progress English version of this preprint can be obtained from the author.