1. Department of Chemistry University of Puerto Rico-Cayey, Antonio R. Barceló Ave. Cayey P.R. 00736.
2. Research and Development Division, ZAYCOR Industries Corporation, 828 de Diego Ave. Caparra Terrace, San Juan PR 00921.
3. Interamerican University, Bayamón Campus, Department of Natural Sciences, Bayamon, Puerto Rico 00957.