The aim of this work is to show the existence of the wave operator and its inverse among Kirchhoff equations and free wave equations.
Kunihiko KAJITANI. "Scattering for one dimensional perturbed Kirchhoff equations." J. Math. Soc. Japan 60 (3) 665 - 693, July, 2008. https://doi.org/10.2969/jmsj/06030665