<\body> Sometimes, a new or better version for a database entry becomes available. This happens for instance, when the value of some field needs to be corrected, or when a paper in a bibliographic database gets published. In , we introduce a few additional attributes and routines for version management of database entries. This is particularly important when entries are attached to files and automatically imported into the databases of other users. In this case, one must be careful to determine the most recent version (or versions) and only update entries when we are sure that the new version is better. In order to achieve this, we use the following principle: each entry comes with a main contributor and for each contributor, we only allow one most recent version. In addition, the current version of a first contributor may be declared to be ``newer'' than the current version of a second contributor. <\description> >Specifies the user who originally contributed the entry. >Specifies the way the entry was contributed ( or ). >A source file in the case when the entry was imported. >Specifies a list of older versions of a given entry. <\explain> <|explain> Create a new version of the entry with identifier (the new version having fields ) and return the identifier of the new entry. <\explain> <|explain> Given an entry with fields , typically from another database, import the entry into our current database. Do the necessary whenever newer versions of this entry already exist in the database (in which case the import is cancelled), or whenever the entry supersedes existing entries.