@article{NUMA_1983__42_132862,
     author = {R. Kre{\ss} and W.T. Spassov},
     title = {On the {Condition} {Number} of {Boundary} {Integral} {Operators} for the {Exterior} {Dirichlet} {Problem} for the {Helmholtz} {Equation.}},
     journal = {Numerische Mathematik},
     pages = {77--96},
     publisher = {mathdoc},
     volume = {42},
     year = {1983},
     zbl = {0534.35027},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1983__42_132862/}
}