Also see : Garfield, E. "Citation Indexes for Science: A New Dimension in Documentation through Association of Ideas."
Science, 122(3159), p.108-11, July 1955

American Documentation 6:31-32, 1955

Citation Indexes for Scientific Literature

W.C. Adair, Manitou Springs, Colorado, U.S.A.

In order to clarify the scope and purpose of this article, it is perhaps well to explain that the writer was for many years the Executive Vice President of the Frank Shepard Company,  publishers of Shepard's Citations, a system of legal research used with great success by lawyers and jurists for over three quarters of a century.  In the course of his incumbency, he has seen occasional requests from members of the medical and engineering professions for information and advice as to whether such a system might not be used in their special fields.  Unfortunately no one connected with the Shepard Company had the time to go into these questions thoroughly.

It was thought that this article describing the functions of citations in the legal profession might indicate to those more familiar with medical or engineering literature, how and whether citations might be used by the researcher in these professions to thread his way through the existing labyrinthine mass of printed materials.

It is necessary to know first that Shepard's Citations is a means of secondary not primary research.  The lawyer briefing a case must cite authorities to back up his arguments.  So must the court in writing its opinions.  This is because of the doctrine of "Stare Decisis" which  means that all courts must follow precedents laid down by higher courts and each count generally also follows its own precedents.  These authorities, of course, are previous cases and the citing of cases is necessary even though a question of statute law is involved.

The lawyer however, must make sure that his authorities are still good law, that is, that the case has not been overruled, reversed, limited or distinguished in some way that makes it no longer useful as a valid authority.  Here is where the use of Shepard's Citations comes in.

A law case is always referred to by volume and page number of the reports wherein it appears.  Thus 301U.S.356 is a reference to the case reported in Volume 301 of the United States Supreme Court Reports on page 356.  Once a case is permanently reported, its reference becomes fixed for all future time.  Likewise statutes are referred to by Chapter and Section number, sometimes by Article, Chapter and Section number of the publication wherein they appear.  Thus Ch.16 Sec.24 N.J.R.S. refers to chapter 16 section 24 New Jersey Revised Statutes.

These permanent references are used in the printed volumes of Shepard's Citations.  Now the lawyer wishing to locate a case or cases for his authority must first of all use a  digest, encyclopedia or other means of original research to get his starting cases.  He uses an index to do this.  Assuming he finds a suitable case or cases to provide his authority, he now refers to Shepard for the purpose of testing his cases to see if they are still good.

By looking up the same volume and page number in Shepard,  will find listed there under all of the subsequent cases right down to date that have cited it as authority.  If it has been reversed or overruled, this fact will be shown by an abbreviation such as "r" or "o" in front of the volume number, as illustrated in the following example:

         101 Mass 210
         112 Mass   65
    e   130 Mass  89
         165 Mass 210
    d   192 Mass  69
         205  Mass 113
    e   212 Mass 173
         221 Mass 210
    a   281 U.S.  63
           35 H.L.R. 76

The above legal citations are completely fictitious but will serve to illustrate how a system of legal citations operates without going into too many legal technicalities.

The case in 101 Massachusetts Reports page 210 is the one we have to start with.  Presumably it has been located through the use of a  digest or other research tool such as an index.  The cases in subsequent volumes listed under it have all cited it and are therefore, in point.  The "e" in front of 130 Mass  89 indicates that in this later case, the former one was explained by the court.  Likewise the legal doctrine laid down in 101 Mass 210 was distinguished as to fact in 192 Mass 69 and limited in 212 Mass 173 to a certain set of facts.  The case was affirmed "a" by the United States Supreme Court so it is still good law.  It was also cited in an article in "HLR" the Harvard Law Review.  Thus at a glance the searcher has all of the subsequent history of the legal doctrine contained in his starting case.

Lawyers and judges have told the writer of experiences in their practice wherein they have won important law suits on the strength of a case located by the use of Shepard which no other method of research disclosed.  The amazing efficiency of the citation method is such that once the starting case or statute is found, it becomes a key that unlocks the entire store of  law on a given point.

It is this function, which it appears, would be of great value in other fields.  An article on any scientific subject would be the key to all others.  It may be objected that a comprehensive index would do the same thing.  It would if the compilers' and users' minds both worked the same way.  Even then, the vast number of titles, sub-titles, cross references, etc. make the most skillfully compiled index difficult to use for the purpose of exhausting a subject.  The index is necessary for a start.  But it can never be the time saver that the citation system is.  Most all lawyers would agree on this.  The index represents the opinion of the compiler as to where a given subject should be pigeonholed.  The list  of citations is essentially determined by the authors, i.e., the courts.

Another objection might be that whereas legal cases and statutes have standard references, scientific articles do not.  This does introduce a difficulty but it is not  insurmountable.  Shepard covers many law reviews and journals and some special publications such as the Journal of the Patent Office Society.  These are given abbreviations and an abbreviation table is shown in the front of the books.

The enormous amount of scientific literature is another obstacle.  It would seem, however, that this could be taken care of  by splitting up the field of science by broad subject matter such as chemistry or medicine and by restricting the number of years covered.

More important than these is the question as to how much do writers on scientific subjects cite other writers and articles.  The writer must assume that they do this to a considerable extent since otherwise there would be little point in the requests for citation systems mentioned earlier.

There probably is no field of human knowledge more comprehensive than the  law.  It touches every area of human activity and its reaches are practically limitless.  Every case that has ever been decided in a court of record is a part of it.  A case, no matter how old, may furnish a lawyer just the argument he needs.  Hence Shepard's Citations embraces every reported case that has ever been decided in this country as well as every statute that has ever been passed by Congress or the various state legislatures.

The volume of literature in a particular area of scientific knowledge might be greater than this but there may not be the need to go back so far in time.

If the ability to start with a certain scientific article and  by means of a chain of citations, to pull up all articles on the same subject would be of value to the researcher in any scientific field, then a citation system appears to be the way to do it.

In closing, courtesy  should be acknowledged to Mr. Eugene Garfield, Associate Editor of American Documentation at whose suggestion this paper was written and who has expressed considerable interest in the question, and has prepared a more detailed paper concerning the implications and application of the Citation system in scientific documentation.