Renata Passos Machado Vieira
Department of Mathematics, Federal Institute of Education, Science and Technology of the State of Ceara, Brazil
Francisco Regis Vieira Alves
Department of Mathematics, Federal Institute of Education, Science and Technology of the State of Ceara, Brazil
Paula Maria
Machado Cruz Catarino
Department of Mathematics, University of Tras-os-Montes and Alto Douro, Portugal