This first "Supplement" to the DOM is both a user manual and a guide to what the Dictionary provides. Like all dictionaries of its kind, the DOM has developed a system of codification of its own in the presentation of the documentary sections. At first glance this may appear a little off-putting. The "Supplement" provides the key. However, for the bibliographic notes (Chapter 4) it has been necessary to adopt a form of presentation which itself requires a key. Chapter 2 expounds the principles behind it, attaining as it does so a degree of complexity which, though formidable, is in fact absolutely imperative.