Strong unique continuation for second order elliptic differential operators
Séminaire Équations aux dérivées partielles (Polytechnique) (1996-1997), Talk no. 3, 15 p. 
@article{SEDP_1996-1997____A3_0,
     author = {Regbaoui, Rachid},
     title = {Strong unique continuation for second order elliptic differential operators},
     journal = {S\'eminaire \'Equations aux d\'eriv\'ees partielles (Polytechnique)},
     publisher = {Centre de math\'ematiques Laurent Schwartz, \'Ecole polytechnique},
     year = {1996-1997},
     note = {talk:3},
     mrnumber = {1482809},
     zbl = {02124105},
     language = {en},
     url = {http://www.numdam.org/item/SEDP_1996-1997____A3_0}
}

Regbaoui, Rachid. Strong unique continuation for second order elliptic differential operators. Séminaire Équations aux dérivées partielles (Polytechnique) (1996-1997), Talk no. 3, 15 p. http://www.numdam.org/item/SEDP_1996-1997____A3_0/

[1] S. ALINHAC, Non-unicite pour des operateurs differentiels a caracteristiques complexes simples , Ann. Sci. E.N.S. 13 (1980), 385-393. | Numdam | MR 597745 | Zbl 0456.35002

[2] S. ALINHAC and M.S. BAOUENDI, A counterexample to strong uniqueness for partial differential equations of Schrödinger’s type, Comm. Partial Differential Equations. 19 (1994) , 1727-1733. | Zbl 0806.35023

[3] L. HÖRMANDER, Uniqueness theorems for second order elliptic differential equations, Comm. Partial Differential Equations. 8(1) (1983), 21-64. | MR 686819 | Zbl 0546.35023

[4] L. HÖRMANDER , “The Analysis of Linear Partial Differential Operators III”, Vol.3 , Springer-Verlag , Berlin/New York , 1985. | Zbl 0601.35001

[5] A. PLIS, On non-uniqueness in Cauchy problem for an elliptic second order differential equation. Bull. Acad. Pol. Sci. 11 (1963), 95-100. | MR 153959 | Zbl 0107.07901

[6] T.WOLFF, A counterexample in a Unique Continuation problem, Comm. Anal. geom. Vol.2 (1) (1994) , 79-102. | MR 1312679 | Zbl 0836.35023