1. Gevrey classes and hypoelliptic boundary value problems;Artino;Pacific J. Math.,1976
2. On semielliptic boundary value problems;Artino;J. Math. Anal. Appl.,1973
3. On, regular hypoelliptic boundary value problems;Barros-Neto;J. Math. Anal. Appl.,1973
4. The parametrix of a regular hypoelliptic boundary value problem;Barros-Neto;Ann. Scuola Norm Sup. Pisa,1972
5. The regularity of solutions of boundary value problems;Hörmander;Acta Math.,1958