ARKERYD, Leif. On $L^p$ Estimates for Quasi-Elliptic Boundary Problems. MATHEMATICA SCANDINAVICA, [S. l.], v. 24, p. 141–144, 1969. DOI: 10.7146/math.scand.a-10926. Disponível em: https://tidsskrift.dk/math/article/view/10926. Acesso em: 14 aug. 2026.