1. Department of MathematicsMorgan State University Baltimore Maryland USA
2. African Institute for Mathematical Sciences (AIMS), P.O. Box 608, Limbe Crystal Gardens, South West Region, Cameroon‐Laboratoire LAMIA, Université des Antilles, Campus Fouillole, 97159, Pointe‐à‐Pitre Guadeloupe (FWI)—Laboratoire MAINEGE, Université Ouaga 3S Ouagadougou Burkina Faso