[1] Alexandrov, A. D.,The Dirichlet problem for the equation, I. Vestnik, Leningrad Univ., 13 (1958), 5-24.
[2] Andersson, J., Weiss, G. S., Cross-shaped and degenerate singularities in an unstable elliptic free boundary problem,
J. Differential Equations, 228 (2006), 633-640.
[3]Bernstein, S. N., Sur la nature analytique des solutions de certaines equations aux derivees parttielles du second order, CR Acad. Sci. Paris, 137 (1903), 778-781.
[4]Bombieri, E., De Giorgi, E., Giusti, E., Minimal cones and the Bernstein problem,
Invent. Math., 7 (1969), 243-268.
[5]Brezis, H., Browder, F., Partial differential equations in the 20th century,
Adv. Math. 135 (1998), 76-144.
[6]Caffarelli, L. A.,The regularity of free boundaries in higher dimensions,
Acta Math.,139 (1977), 155-184.
[7]Caffarelli, L. A.,The obstacle problem revisited,
J. Fourier Anal. Appl.,4 (1998), 383-402.
[8]Caffarelli, L. A., Cabre, X.,
Fully Nonlinear Elliptic Equations, American Mathematical Society Colloquium Publications, vol. 43, American Mathematical Society, Providence, RI, 1995.
[9]Cabre, X., Caffarelli, L. A.,
Interior C2,a regularity theory for a class of nonconvex fully nonlinear elliptic equations,
J. Math. Pures Appl., 82 (2003), 573-612.
[10]Calderon, A. P., Zygmund, A., On the existence of certain singular integrals, Acta Math., 88 (1952), 85-139.
[11]De Giorgi, E., Sulla differenziabilitae l’analiticita delle estremali degli integrali multipli regolari,
Mem. Accad. Sc. Torino, C. Sc. Fis. Mat. Natur., 3 (1957), 25-43.
[12]De Giorgi, E., Una estensione del teorema di Bernstein, Ann. Scuola Norm. Sup. Pisa Cl. Sci., 19
(1965), 79-85.
[13]De Giorgi, E., Una estensione del teorema di Bernstein, Ann. Scuola Norm. Sup. Pisa Cl. Sci., 19
(1965), 79-85.
[14]Federer, H., The singular sets of area minimizing rectifiable currents with codimension one and
of area minimizing flat chains modulo two with arbitrary codimension, Bull. Amer. Math. Soc., 76
(1970), 767-771.
[15]Fleming, W. H., On the oriented Plateau problem, Rend. Circ. Mat. Palermo (2), 11 (1962), 69-90.
[16]Figalli, A., Joaquim S., On the fine structure of the free boundary for the classical obstacle problem,
Invent. Math., 215 (2019), 311-366.
[17]Frehse, J., On the regularity of the solution of a second order variational inequality, Boll. Un. Mat.
Ital. (4), 6 (1972), 312-315.
[18]Hilbert, D., Über das Dirichletsche Princip, Jahresber. Deutsch. Math.-Verein.-Vereinigung, 8
(1900), 184-187.
[19]Hopf, E., Zum analytischen Charakter der Lösungen regulärer zweidimensionaler Variationsprobleme,
Math. Z., 30 (1929), 404-413.
[20]Hopf, E., Über den funktionalen, insbesondere den analytischen Charakter der Lösungen elliptischer
Differentialgleichungen zweiter Ordnung, Math. Z., 34 (1932), 194-233.
[21]Ishii, H., On uniqueness and existence of viscosity solutions of fully nonlinear second‐order elliptic
PDE’s, Comm. Pure Appl. Math., 42 (1989), 15-45.
[22]Kinderlehrer, D., Nirenberg, L., Regularity in free boundary problems, Ann. Scuola Norm. Sup.
Pisa Cl. Sci., 4 (1977), 373-391.
[23]Lichtenstein, L., Über den analytischen Charakter der Lösungen Zweidimensionaler Variationsproblem,
Bull. Acad. Sci. Cracovie Cl. Sci. Mat. Nat. A (1912), 915-941.
[24]Morrey Jr., C. B., On the solutions of quasilinear elliptic partial differential equations, Trans. Amer.
Math. Soc., 43 (1938), 126-166.
[25]Moser, J., A new proof of De Giorgi’s theorem concerning the regularity problem for elliptic
differential equations, Comm. Pure Appl. Math., 13 (1960), 457-468.
[26]Nash, J., Continuity of solutions of parabolic and elliptic equations, Amer. J. Math., 80 (1958),
931-954.
[27]Nadirashvili, N., On Stationary Solutions of Two-Dimensional Euler Equation, Arch. Ration.
Mech. Anal., 209 (2013), 729-745.
[28]Nadirashvili, N., Vlădut, S., Nonclassical solutions of fully nonlinear elliptic equations, Geom.
Funct. Anal., 17 (2007), 1283-1296.
[29]Newson, M. W., Mathematical problems: Lecture delivered before the international congress of
mathematicians at Paris in 1900 by Professor David Hilbert, Bull. Amer. Math. Soc., 8 (1902),
437-479.
[30]Petrowsky, I. G., Sur l’analyticité des solutions des systèmes d’équations différentielles, Rec.
Math. Moscou, (2) 5 (1939), 3-70.
[31]Schaeffer, D. G., Some examples of singularities in a free boundary, Ann. Scuola Norm. Sup. Pisa,
4 (1977), 133–144.
[32]Shahgholian, H., C1,1 regularity in semilinear elliptic problems, Comm. Pure Appl. Math., 56
(2003), 278-281.
[33]Simons, J., Minimal varieties in riemannian manifolds, Ann. of Math., (2) 88 (1968), 62-105.
[34]Stefan, J., Über einige Probleme der Theorie der Wärmeleitung, Aus den Sitzungsberichten d. kais.
Akademie d. Wissenschaften in Wien. Mathem.-naturw. Classe, 1889, XCVIII, Abth. II. a., 1889,
473-484.
[35]Uraltseva, N. N., Regularity of solutions of multidimensional elliptic equations and variational
problems, Dokl. Akad. Nauk, 130 (1960), 1206-1209.
[36]Weyl, H., The method of orthogonal projection in potential theory, Duke Math. J., 7 (1940), 411-444.
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