This bibliometric study examined 19,385 citations in the bibliographies, book reviews, and reading lists of 70 volumes of Adult Education Quarterly, Adult Education, Adult Education Bulletin, Adult Education Journal, and Journal of Adult Education, and 13 volumes of the Handbook of Adult Education in the United States to identify books published before 1960 which have been frequently cited before and after 1960. Through citation analysis, an initial list of 434 titles was reduced to a core list of 64 books cited five times or more during the years between 1934 and 1988. For the purposes of this study, numbers of citations were taken to mean importance of works by indicating usefulness to subsequent authors. Of the 64 books, 55 had received at least one citation before 1960 and 57 had received at least one citation after 1960. While not all 64 of the core works constitute what might be called "classic works," it is suggested that classic works are likely to be found within the listed works.