Electronic Journal of Differential Equations,
Vol. 2002(2002), No. 87, pp. 1-13.

Title: On the Keldys-Fichera boundary-value problem for degenerate
       quasilinear elliptic equations
        
Authors: Zu-Chi Chen (Univ. of Science and Technology of China)
         Ben-Jin Xuan (Univ. Nacional, Bogota, Colombia)
         
Abstract: 
  We prove existence and uniqueness theorems for the
  Keldys-Fichera  boundary-value problem using
  pseudo-monotone operators.
  The equation studied here is quasilinear, elliptic, and
  its set of degenerate points may be of non-zero measure.
  We also obtain  comparison and  maximum  principles
  for this problem.
     
Submitted April 27, 2002. Published October 10, 2002.
Math Subject Classifications: 35J65, 35J30.
Key Words: Keldys-Fichera; existence; uniqueness; maximum
principle;
           comparison principle.