Affiliation: | Institute of Mathematics, Federal University of Rio de Janeiro, 21945 970, Rio de Janeiro, RJ, Brazil e-mail: anatoli@dmm.im.ufrj.br, BR Mathematical Department, State University of Norte Fluminense, 28015 620, Campos dos Goytacazes, RJ, Brazil e-mail: wilma@uenf.br, BR Mechanical Engineering Program, COPPE/Federal University of Rio de Janeiro, 21945 970, Rio de Janeiro, RJ, Brazil e-mail: jose@com.ufrj.br, BR
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