  Some field theoretical aspects, such as the effective action and Schwinger
pair production, are critically reviewed in strong QED. The difference of the
boundary conditions on the solutions of the field equation is discussed to
result in the effective action both in the Coulomb and time-dependent gauge.
Finally, the apparent spin-statistics inversion is also discussed, where the
WKB action for bosons (fermions) works well for fermion (boson) pair-production
rate.
