GRUBB, Gerd. Remainder estimates for eigenvalues and kernels of pseudo-differential elliptic systems. MATHEMATICA SCANDINAVICA, [S. l.], v. 43, p. 275–307, 1978. DOI: 10.7146/math.scand.a-11781. Disponível em: https://tidsskrift.dk/math/article/view/11781. Acesso em: 14 aug. 2026.