“…One refers, for instance, to [76] and the references therein. Many interesting mathematical works have dealt with different aspects of time-reversal phenomena: see, for instance, [44,45] for time-reversal in the time-domain, [65,66,73,128] for time-reversal in the frequency domain, [53,79] for time-reversal in random media, and [4,6,104] for time-reversal in attenuating media. The results provided in this chapter on time-reversal techniques are from [4].…”