Dragonfly ID Book

[Ron Lane]

Can someone recommend a good field guide or 2 for the identification
of these insects. While we were out lepping, we went by a marsh which
we like to investigate periodically for Baltimores and others and were
astounded by the diversity of dragonflys. I know I've read that other
leppers have also started to ID and track dragonflys and thought I
might get some help here.
Ron