[Jabref-users] Warning Needs Explanation

[Rich S. <rsh...@ap...>]

   Running version 2.9.2 here (2.10 does not properly display groups). When I
invoke the application a warning message window displays:

'1. empty bibtex key: Hron and Filz: "NA" (N/A) (grouping may not work for
this entry)'

   There is only one entry for Hron and Filzmoser, and that record has a
bibtex key: Hron2013.

   What is this warning message actually trying to tell me?

Rich