[1] Univ Claude Bernard Lyon 1, Univ Jean Monnet, Ecole Cent Lyon, ICJ UMR5208,CNRS,INSA Lyon, F-69622 Villeurbanne, France
[2] Univ Coll Dublin, Sch Math & Stat, Belfield Campus, Dublin, Ireland
[3] Romanian Acad, Inst Math, 21 Calea Grivitei St, Bucharest 010702, Romania
[4] Higher Inst Appl Math & Comp Sci Kairouan, Ave Assad Iben Fourat, Kairouan 3100, Tunisia