@techreport{DeuflhardFrieseSchmidt1997, author = {Peter Deuflhard and Tilmann Friese and Frank Schmidt}, title = {A Nonlinear Multigrid Eigenproblem Solver for the Complex Helmholtz Equation}, institution = {ZIB}, address = {Takustr. 7, 14195 Berlin}, number = {SC-97-55}, language = {eng}, year = {1997} }