My specific interest in citation data for historical research has focused on the role of the computer in constructing historical “maps.” The development of many sophisticated computer programs employing the critical path methodology for the Project Evaluation Review Technique (PER’Q 18.19 stimulated the further pursuit of the now proposed technique in which the computer actually draws the topological network diagrams which show the chronological and derivational relationships between Scientflc papers and therefore scientific discoveries.

One purpose of this communication is to record my forewarning concerning the possible promiscuous and careless use of quantitative citation data for sociological evaluations, including personnel and fellowship selection. In particular, I wish to disassociate myself from such abuse of citation data recently imputed to my by Swanson. He erroneously stated that in my 1955 paper in Science 1 I claimed one could measure the importance of a paper by citation counting. Citation counting is an old technique and has been criticized for many reasons by Brodman, Raisig, and others. Impact is not the same as importance or significance. There is no specific correlation between the number of papers published by an individual and the quality or importance of his work, though Price has indicated that scientists who produce work of high quality usually have a high publication rate. We can confirm this and add the observation that their papers usually are also cited more frequently than the average. [...] Citation indexes can be used to facilitate personnel and fellowship evaluation simply because they provide more convenient access to the literature. Citation indexes synthesize a consensus of scientific opinion needed in a careful appraisal of research, whether for editorial refereeing, making awards, or selecting personnel. It is preposterous to conclude blindly that the most cited author deserves a Nobel prize. On this basis, LYsenko and others might have been judged the greatest scientists of the last decade. Such quantitative data can have significance for the historian who can carefully evaluate all the data available. Surely, the history of science must record the controversial as well as the non-controversial figure. However, the mere ranking by numbers of citations or the numbers of papers published is no way to arrive at objective criteria of importance.

...interest in using citation indexes for retrieval and dissemination is equaled, if not exceeded, by the interest in its use for sociological and historical research. Indeed, Newell stated: ‘ ‘Ci-tation Indexing will generate a spate of empirical work on the sociology of sci- ence..., It is rather easy to predict, I think, that the publication and wide availability of an extensive citation in- dex will have strong social consequences along the line of becoming a controlling variable for the advancement and employment of scientific personnel . . . . It makes little difference whether one likes this or not.’

One can also program the computer to “erase” one or more nodes and its connections in the network. By making the assumption that any papers which derive from these nodes should also be erased, one can then determine whether an alternate “critical path” to a subsequent discovery does exist. Thus, one can legitimately ask whether the work of Whitnah on the physical properties of milk22 or Elworthy ’s work on lecithin micelles23 would have been possible if Einstein had not published his paper on measuring dimensions of molecules! 24 Further, by counting the totaJ number of “terminal” nodes erased, onc may possibly obtain a useful quantitative measure of historical impact. A terminal node is a member of a particular set of papers, as, e.g., all 1962 papers. The critical impact of Einstein’ s work would be the percentage of 1962 papes which, one assumes, would not have been written if they could not have cited either Einstein’s papers or papers which have cited Einstein. In making such calculations, one has to also consider the papers cited by Einstein.