sentence1: the long time asymptotics for nonlinear wave equations have been the subject of intensive research , starting with the pioneering papers by segal , where the nonlinear scattering and local attraction to zero were considered .
sentence2: the long time asymptotics for nonlinear wave equations have been the subject of intensive research , starting with the pioneering papers by segal , where the nonlinear scattering and the local attraction to zero solution were proved .