M. Costabel et M. Dauge, CONSTRUCTION OF CORNER SINGULARITIES FOR AGMON-DOUGLIS-NIRENBERG ELLIPTIC-SYSTEMS, Mathematische Nachrichten, 162, 1993, pp. 209-237
Corner singularities in plane domains are characterized by certain sin
gular exponents and angular functions. Our construction of singulariti
es is based on two Cauchy integrals at two different levels of symboli
c calculus. This construction yields new information about the angular
functions and also more explicit formulas for the computation of the
singular exponents.