A Secure Payment System for Electronic Commerce. - Ioannis Mavridis; George Pangalos; Triadafyllos Koukouvinos; Sead Muftic (DEXA Workshop, 1999)

Classification of nilpotent lie algebras of dimension nine whose maximum abelian ideal is of dimension seven. - G. Tsagas; A. Kobotis; Triadafyllos Koukouvinos (Int. J. Comput. Math., 2000)