• Hipoeliticidade global e vetores simultaneamente aproximáveis. 

      Simsen, Jacson; http://genos.cnpq.br:12010/dwlattes/owa/prc_imp_cv_int?f_cod=K4766006A9 (Universidade Federal de São Carlos, UFSCar, Programa de Pós-graduação em Matemática, , 11/08/2003)
      A necessary and sufficient condition is given for a sum of squares operator to be globally hypoelliptic. This condition is expressed in terms of Diophatine approximation properties of the coefficients. The proof of the ...