This section identifies several occupation-classification manuals. The purpose of these manuals is to define occupations in a standard way that enables international comparison and sharing of data. They are frequently produced by statistical agencies and may be associated with censuses, which is why they are included in this guide. Four for Bulgaria are listed below, but not annotated. Select any title described below to view full bibliographic information for that item in the Library of Congress Online Catalog. Links to full electronic versions are provided when available.