Sorry for the mistake: I wrote one \ too many so that I unwittingly created an absurd link.
The message was supposed to be this:

Hi all,

To include in a text several graphics that for some reason must have the same figure number (with suffixes .a, .b etc.), I use
\startplacefigure[location=here,reference=,title={},group=,groupsuffix=]
{\externalfigure[]}
\stopplacefigure
an experimental solution that Hans gave me in april (Ref. ntg-context Digest, Vol 106, Issue 4, Date:14 April 2013) and which works perfectly.

My problem is: how can I refer in my text to this set of figures (instead of to the separate figures). I have tried to use "group" as the label for referencing, as it is the only argument that all figures have in common, but my trials failed and I have no idea how to accomplish this. (The wiki is too vague for me on this point.)

Thanks in  advance for any help.

Regards, 
Robert Blackstone