1. Adolfsson, V.: L
2 integrability of second order derivatives for Poisson equations in nonsmooth domain. Math. Scan., 70, 146–160 (1992)
2. Agranovich, M. S.: Sobolev Spaces, Their Generalizations and Elliptic Problems in Smooth and Lipschitz Domains, Springer Monographs in Mathematics. Springer-Verlag, 2015
3. Awanou, G., Lai, M. J., Wenston, P.: The multivariate spline method for numerical solution of partial differential equations, in: Wavelets and Splines, Nashboro Press, Brentwood, 24–74 (2006)
4. Brenner, S. C., Scott, L. R.: The Mathematical Theory of Finite Element Methods, Springer-Verlag, New York, 1994
5. Caccioppoli, R.: Limitazioni integrali per le soluzioni di unequazione linear ellittica a derivate parziali. Giornale di Bataglini, 80, 186–212 (1950–51)