This frequency-domain response problem leads to an  system of linear equations as described above. An early description of a frequency-domain response FDTD method to solve scattering problems was published by Christ and Hartnagel (1987).
This frequency-domain response problem leads to a system of linear equations, which is similar to the concept of a frequency-domain response FDTD method used to solve scattering problems as described by Christ and Hartnagel (1987).