From time to time, you may find that common functions like CurrentDB, Str$ or Mid$ stop working. This condition is usually caused by a reference error in the database. (All Access databases contain references, which are a way of referring to another application's or project's type library. In general, you want to ensure that the files referenced in an Access application exist in exactly the same location on the client workstations as they did on the development workstation, and that each referenced file is the same version on all workstations.) Avoiding reference issues require an understanding of how libraries are referenced in an Access database and what is needed to install a database on a target machine without breaking these references.