The CERL Thesaurus File is a unique facility developed to address the particularly European issue that place name and personal names in Europe varied from country to country in the period of hand press printing (1450 - c. 1830). As such, it is an essential research tool for scholars and researchers of the period. The CERL Thesaurus file contains forms of imprint places, imprint names, personal names and corporate names as found in material printed before the middle of the nineteenth century - including variant spellings, forms in Latin and other languages, and fictitious names. Authority files contributed by CERL member libraries and other libraries/projects concentrating on the history of the book are brought together and made searchable in one single system . The CERL Thesaurus merges standard and authority forms of names that are used in present day library catalogues without imposing CERL’s own authoritative form of name. Instead, standard and variant forms are listed alphabetically with a clear indication of the institutions that use a particular standard form.