“…Several reviews of the field by Hochstrasser and Prasad (15), Kopelman (4), Levinson and Rashba (66), and Toyozawa (67) have appeared. A number of diverse aspects of the problem have been examined, such as, polarons (68)(69)(70)(71), charge carrier-lattice interaction and photoconductivity (72-7^), weakly allowed transitions (75)(76), coupling in one-dimensional chains (77,78), retarded interactions (79), Urbach rule effects (80)(81)(82)(83)(84)(85)(86) and line shapes (87-100). Strong and weak coupling models (101)(102)(103)(104)(105)(106)(107)(108)(109) for Frenkel excitons and phonons have been discussed at length.…”