The bibutils program set interconverts between various bibliography 
formats using a common MODS-format XML intermediate. For example, 
one can convert RIS-format files to Bibtex by doing two 
transformations: RIS->MODS->Bibtex. 

By using a common intermediate for N formats, only 2N programs are 
required and not N^2-N. These programs operate on the command line 
and are styled after standard UNIX-like filters.

Bibutils converts between bibliography formats including BibTeX, 
RIS, Endnote (Refer), ISI, COPAC, and Medline XML using a 
MODS v3.0 XML intermediate.