1. Contribution #120 from the Center for Photochemical Sciences.
2. ?Three Dimensional Modeling,? Internal Report 3M Co.; private communication.
3. U.S. Patent 4,575,330 (March 11, 1986).
4. This model is that of 3D Systems; Avenue Hall, Valencia, Calif.
5. Eox + Ered + Eexcited state = allowed algebraic energy sum.