In summary, as more and better quality measurements of magnetic, electric and
electromagnetic fields are being made in the epicentral regions of earthquakes and
on volcanoes around the world, it is clear that observed field perturbations are
generated by a variety of source processes. It is also clear from this review that
there are many problems which, if not addressed, will soon reflect on the credibility
of this field of geophysics. Particular problems needing work include: