1. Facultad de Farmacia, Universidad Central de Venezuela, Caracas, Venezuela
2. University of Michigan Herbarium and Department of Ecology and Evolutionary Biology, Ann Arbor, Michigan, USA
3. Escuela de Química, Facultad de Ciencias, Universidad Central de Venezuela
4. Dipartimento di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università di Roma, Roma, Italy