Subject: categories: reference: normal categorical subgroup?

From: Marco Mackaay <[email-masked]>
Date: Fri, 9 Feb 2001 11:02:52 +0000 (GMT)

To all category theorists,

I'm looking for a reference to the definition of a normal categorical 
subgroup, i.e. the right kind of subgroupoid of a categorical group for
taking the quotient. I know the definition, but I have no reference. Does
anyone know a published origin of the definition?

Best wishes,

Marco Mackaay