1MATHEMATICS DEPARTMENT, UNIVERSITY OF Hawall aT HILo, 200 W. Kawi Sr., Hito, Hawan 96720, USA.
2COLLEGE OF HUMANITIES AND SCIENCES, NIHON UNIVERSITY, 3-25-40 SAKURAJOSUI SETAGAYA-KU, TOKYO 156-8550, JAPAN.
3DEPARTAMENT DE MATEMATICA APLICADA I TELEMATICA, UNIVERSITAT POLITECNICA DE CATULUNYA, 08071 BARCELONA, SPAIN.