Page 106 - Textos de Matemática Vol. 43
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94 RICARDO PEREIRA, PAULA ROCHA AND RITA SIMO˜ES
(R. Pereira and R. Sim˜oes) Department of Mathematics University of Aveiro
Aveiro
Portugal
E-mail address: ricardopereira@ua.pt, ritasimoes@ua.pt
(P. Rocha) Department of Electrical and Computer Engineering Faculty of Engineering
University of Oporto
Porto
Portugal
E-mail address: mprocha@fe.up.pt
