Takamichi Saito Akio Morii Tadashi Komori Toshiyuki Kito Fumio Mizoguchi Anti-spam mail system. 99-108 2006 37 Systems and Computers in Japan 13 http://dx.doi.org/10.1002/scj.10627 db/journals/scjapan/scjapan37.html#SaitoMKKM06