[NTG-context] Using key as numbering in \placepublications

Hi, I'm writing my thesis using ConTeXt but I'm not satisfied with the way the publication list is displayed. I'd like to display the key, in brackets, in front of every publication in the list (i.e. replace the [2] numbering in front of it by [Sha07] for example). The numbering option only offers yes, no, short and bib. I'd like a "key" option. How can I achieve that? Any clue, example and/or suggestion is welcome, Thanks in advance, Antoine