  A classical theory of a radiating two-dimensional crystal is proposed and an
expression for the radiative-reaction electric field is derived. This field
plays an essential role in connecting the microscopic electromagnetic fields
acting on each dipole of the crystal to the macroscopic one, via the boundary
conditions for the system. The expression of the radiative-reaction electric
field coincides with the macroscopic electric field radiating from the crystal
and, summed to the incident electric field, generates the total macroscopic
electric field.
