Reference publication year spectroscopy (RPYS) of papers published by Loet Leydesdorff: A giant in the field of scientometrics passed away.

Loet Leydesdorff (mentioned as Loet in the following) passed away in March 2023. Our paper is dedicated to the important contributions of this exceptional researcher (in scientometrics). We investigated which studies, theories, methods, and ideas have influenced Loet's scientific work. The method reference publication year spectroscopy (RPYS) can be used to answer this and related questions. Many RPYS studies have been published regarding the historical roots of research fields, journals, and scientists. The program CRExplorer was specifically developed for RPYS. In this study, we used CRExplorer to investigate the historical roots and influential publications of Loet's oeuvre. The results demonstrate the wide range of topics in Loet's research and their fundamental meaning for the scientometric field. [ABSTRACT FROM AUTHOR]