bations has been extensively investigated and already reached a satisfactory stage, while few have been known about long-range scattering for classical wave equations. It is well known (cf., e.g., Reed-Simon [17] and Mochizuki [14]) that the Schrodinger and classical wave equations are related by the invariance principle of Kato and Birman theory in short-range scattering and it has been expected that also in long-range scattering the invariance principle allows us to treat clas-