[NTG-context] en-dash for ranges of numbers in Bibliographies

Hi, in BibTeX databases ranges of numbers are usually listed with a single dash (e.g. 3-7) for compatibility reasons. Therefore the standard BibTeX styles convert a single dash in page numbers or range of numbers to a double dash (3--7). How do I get the same behaviour for \volume \issue \pages in the bibliographic module? Thanks! Cheers, Florian