1. GLOBAL NONEXISTENCE OF SOLUTIONS TO SYSTEM OF KLEIN-GORDON EQUATIONS WITH DEGENERATE DAMPING AND STRONG SOURCE TERMS IN VISCOELASTICITY. Authors: FARES YAZID, DJAMEL OUCHENANE, KHALED ZENNIR.2. GLOBAL NONEXISTENCE OF SOLUTION FOR COUPLED NONLINEAR KLEIN-GORDON WITH DEGENERATE DAMPING AND SOURCE TERMS. Authors: DJAMEL OUCHENANE, ZINEB KHALILI, FARES YAZID.3. LOCAL EXISTENCE AND BLOW UP OF SOLUTIONS TO A LOGARITHMIC NONLINEAR WAVE EQUATION WITH TIME-VARYING DELAY. Authors: ABDELBAKI CHOUCHA, DJAMEL OUCHENANE.4. EXPONENTIAL GROWTH OF SOLUTIONS WITH LP-NORM OF A NONLINEAR VISCOELASTIC WAVE EQUATION WITH STRONG DAMPING AND SOURCE AND DELAY TERMS. Authors: DJAMEL OUCHENANE, ABDELBAKI CHOUCHA.5. GLOBAL NONEXISTENCE OF SOLUTIONS TO A LOGARITHMIC NONLINEAR WAVE EQUATION WITH INFINITE MEMORY AND DELAY TERM. Authors: ABDELDJABAR BOUREGA, DJAMEL OUCHENANE.