Discussion of retrieval overlap and relevant overlap focuses on an analysis of data from an earlier study on overlap among document representations. This new analysis investigated the odds that an item was judged relevant when it was retrieved by two search fields as opposed to being retrieved by only one field. (Contains 17 references.) (LRW)

Using examples of data from the areas of information retrieval and of multivariate data analysis, six hierarchic clustering algorithms (single link, median, centroid, group average, complete link, Wards's) are examined and evaluated by using three proposed coefficients of hierarchic structure. Nine references are cited. (EJS)

Estimates of frequency of spelling errors are made based on a sample of 3,600 index terms drawn from 11 bibliographic data bases. The impact of these errors is discussed by tape supplier, tape user, and end user; with some suggestions for search strategies.