From its first edition the purpose of Walford has been to identify and evaluate the widest possible range of reference materials. No rigid definition of reference is applied. In addition to the expected bibliographies, indexes, dictionaries, encyclopaedias, and directories, a number of important textbooks and manuals of general practice are included. While the majority of the items are books, Walford is a guide to reference material. Thus periodical articles, microforms, online and CD-ROM sources are all represented. In this volume a particular effort has been made to improve coverage of the latter two categories. To be of manageable proportions a guide such as this must inevitably be selective. Most major reference tools are included, whenever originally published, provided they remain useful. New material, often overlooked, is also covered in some depth. The geographic scope is international, but with an emphasis on English-language material. A special effort has been made to ensure that the output of small and specialist publishers is not neglected. Entries in Walford follow a subject arrangement based on the Universal Decimal Classification Medium Edition of 1985 (BS1000M). Subject access for users unfamiliar with UDC can be gained either by checking the contents page to find the relevant section and then browsing through the entries which are subdivided by form, place etc, or by using the subject index. Terms in this index are generated by the classification numbers given to each entry. References in the accompanying author/title index are to entry rather than UDC or page numbers, each record being assigned a consecutive number. Full instructions on the structure and use of the indexes can be found in their introduction. Individual entries in Walford are nearly always based on the examination of the actual item and include full bibliographic detail, ISBN and, if in print, the price when it can be ascertained. Brief critical annotations are provided in most cases, giving summary publishing, outline of contents, comparison with other works, especially notable features and a brief general assessment of overall value, often illustrated by quotations from or references to reviews.