|  | 
 [35J25] 
Boundary value problems for second-order, elliptic equations 
 
  - Castro, L.P.,
 
    Strongly Elliptic Operators for a Plane Wave Diffraction Problem in
    Bessel Potential Spaces, Volume
    3, Issue 2, Article 25,
    2002. [002_01] 
       
  - Le, V.K.,
 
    Sub-super Solutions and the Existence of Extremal Solutions in
    Noncoercive Variational Inequalities, Volume
    2, Issue 2, Article 20,
    2001. [033_00] 
 
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