The backrefx package is now obsolete after the release of backref v1.23, because all the functionality of backrefx is now provided by backref. This release of backrefx is only provided for backward compatibility of existing documents.

The backrefx package enhanced the backref package of David Carlisle and Sebastian Rahtz. It enables backref to print the bibliographic back references in a more typographically sound manner (similar to the back references in TeX Unbound of Hoenig), for example: (Cited on page 10.) (Cited on pages 10 and 12.) (Cited on pages 10, 12 and 15.)

The author is Danie Els.