Acknowledgements

I am very thankful to Prof.Y.Shimizu, Prof.S.Yamada and Prof.K.Tokushuku for their useful comments and various supports. I shall never forget the collaboration with the members of the Minami-Tateya group at KEK; J.Fujimoto, T.Ishikawa, T.Kaneko, K.Kato, S.Kawabata, T.Kon, Y.Kurihara, H.Tanaka and T.Watanabe. I also wish to thank the conveners of the working group on QED radiative effects in HERA Monte Carlo Workshop at DESY; L.Favart, S.Schlenstedt and H. Spiesberger for the helpful discussions. This work was supported in part by the Japanese Ministry of Education, Science and Culture(the Monbusho) and its grant for Scientific Research (No.11206203).