1. ON THE EXISTENCE OF POSITIVE SOLUTIONS OF A CLASS OF PARABOLIC REACTION DIFFUSION SYSTEMS. Authors: MOUNIR REDJOUH, SALIM MESBAHI.2. INVARIANT REGIONS AND GLOBAL EXISTENCE OF UNIQUENESS WEAK SOLUTIONS FOR TRIDIAGONAL REACTION-DIFFUSION SYSTEMS. Authors: NABILA BARROUK, KARIMA ABDELMALEK, MOUNIR REDJOUH.