@article{NUMA_1983__42_132860,
     author = {Ludwig Wagatha},
     title = {Approximation of {Pseudodifferential} {Operators} in {Absorbing} {Boundary} {Conditions} for {Hyperbolic} {Equations.}},
     journal = {Numerische Mathematik},
     pages = {51--64},
     publisher = {mathdoc},
     volume = {42},
     year = {1983},
     zbl = {0536.35047},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1983__42_132860/}
}