“…Recently, this kind of analysis has often been linked to the term "Reference Publication Year Spectroscopy (RPYS)", which was coined in the study of cited references in research papers carried out by Marx et al [1] and further elaborated in other analyses conducted by Barth et al, [2] Bornmann and Marx, [3] Leydesdorff et al, [4] Thor et al, [5,6] Marx et al, [7] or Thor et al [8] One of the main goals of RPYS is to identify the so-called historical roots (origins), milestones, or landmark papers in a certain scientific discipline, journal, or region. To this end, Bornmann et al [9] applied the RPYS method to the publications by a single researcher (Eugene Garfield), Haunschild [10] to a specific journal (Information), Ballandonne and Cersosimo [11] to a group of journals in management, economics, and finance, Comins and Hussey [12] to global positioning system (GPS) papers, Comins and Leydesdorff [13] to biomedical research, and Fiala and Bornmann [14] to Eastern European computer science research. Furthermore, by means of RPYS, Elango et al [15] detected the historical roots of tribology research, Hou [16] of citation analysis, Li et al [17] of various research fields in China, Khasseh and Mokhtarpour [18] of the field of knowledge management, Millán et al [19] of social psychology in Brazil, Wray and Bornmann [20] of philosophy of science, and Yeung and Wong [21] of visual analogue scale in psychology.…”