Reviews : van Rijsbergen, C. J. Information retrieval. 2nd edn. London, Butterworths, I978. 208pp

workers. It makes simple use of some advanced mathematics, and certainly expects a mathematical orientation on the part of the reader. This second edition incorporates a new chapter on probabilistic retrieval, to supplement the original coverage of automatic text analysis, automatic classification, file structures, search strategies and evaluation. There is a copious bibliography. The value of a text such as this for the practising designer, operator or searcher of a retrieval system is to provide insights into basic characteristics of the entities and processes involved-words in documents, keywords, queries, files, search, feedback, output-and in particular their &dquo;computable&dquo; characteristics on which