This section is intended to give a brief and intuitive overview
of the theoretical research we conducted in order to implement the Kirchhoff
migration/inversion technique. It is *not* intended to give
rigorous derivations or proofs! Readers interested in the latter can
refer to Lumley *et al.* (1991), and subsequent SEP reports,
in which the full mathematical details are to be expounded.

12/18/1997