Least Squares Approximations to First Order Elliptic Systems
Publications mathématiques et informatique de Rennes no. S4  (1977), article no. 11, 14 p.
@article{PSMIR_1977___S4_A11_0,
     author = {Nitsche, J. A.},
     title = {Least Squares Approximations to First Order Elliptic Systems},
     journal = {Publications math\'ematiques et informatique de Rennes},
     publisher = {D\'epartement de Math\'ematiques et Informatique, Universit\'e de Rennes},
     number = {S4},
     year = {1977},
     language = {en},
     url = {http://www.numdam.org/item/PSMIR_1977___S4_A11_0}
}
Nitsche, J. A. Least Squares Approximations to First Order Elliptic Systems. Publications mathématiques et informatique de Rennes, no. S4 (1977), article  no. 11, 14 p. http://www.numdam.org/item/PSMIR_1977___S4_A11_0/

[1] Haack, W. and G. Hellwig Die Überführung des Randwertproblems für Systeme elliptischer Differentialgleichungen auf Predholmsche Integralgleichungen I. Math. Nachr. 4 (1950-1951), 408-418 | MR 41327 | Zbl 0042.10404

[2] Nitsche, J.A. A projection method for Dirichlet-Problems using subspaces with nearly zero boundary conditions in "The mathematical foundations of the finite element method with application to partial differential equations", K. Aziz and I. Babuska eds., Acad. Press, New York and London, 1972, 603-627 | MR 426456 | Zbl 0271.65059

[3] Vekua, I.N. Generalized Analytic Functions. Pergarnon Press, Oxford (1962). | MR 150320 | Zbl 0100.07603