The Law of Constant Citation for Scientific Literature

In listing the literature concerning the subject of ‘vibrating plates’ the following law was noticed: Rj x aj,t=constant=5·6 where Rj is the ‘citation factor’ for the year, j, and aj,t stands for the total number of articles that have appeared up to and including year j. ‘This ‘citation law’ is based on the remarkable fact that in more than 150 years the mean number of relevant citations per article per year has remained constant, viz. 2·8, in spite of the fact that after 1950 three times as many articles have been published as in the period before 1950.