In 1964 Eugene Garfield and the Institute for Scientific Information published the first Science Citation Index in five printed volumes, indexing 613 journals and 1.4 million citations, using the method of citation analysis. When he launched the Science Citation Index Garfield published an extensive paper entitled "Science Citation Index"--A New Dimension in Indexing, Science, 144 (May 8, 1964) 659-654.
Two years later Science Citation Index became available on magnetic tape.
As Garfield, wrote in 1979, the Science Citation Index was initially modeled after Shepard's legal citation system. See Garfield, Citation Indexing—Its theory and application in science, technology, and humanities (New York: John Wiley & Sons, 1979), Chapter 2: A Historical View of Citation Indexing, 7ff.