Changing Sources of Published Information

We looked at the types of references in papers published during the first month of 1972, 1982, and 1992 in the Astrophysical Journal and Astronomy & Astrophysics; also those published in the former journal during the first half-years of 1952 and 1962. Some of the results are qualitatively predictable, such as the decrease (from 12% to 1%) in references to observatory publications and inhouse technical reports, and the increase (from 1% to 10%) in references to conference papers. But what are surprising are (1) the low (less than 3%) reference rate to preprints, showing that they are not replacing journal papers (78%) as the primary source for reliable information, (2) the low (1%) reference rate to theses, showing that they are not cited more frequently than average research papers, (3) the low (1%) reference rate to review papers, showing that contrary to popular belief, very few people cite review papers instead of the original research papers, and (4) the slightly decreasing reference rate (from 6% to 4%) to monographs, showing that despite their greatly increased publication rate, they are gradually being quoted less for research use (as contrasted to tutorial use).