Abstract Scattering Theory for Time-Periodic Systems with Applications to Electromagnetism J. CooperWalter Strauss Indiana University Mathematics Journal 1985 text pdf 10.1512/iumj.1985.34.34003 10.1512/iumj.1985.34.34003 en Indiana Univ. Math. J. 34 (1985) 33 - 83 state-of-the-art mathematics http://iumj.org/access/