Information Processing Letters
Information Processing Letters > 1997 > 62 > 6 > 301-303
Information Processing Letters > 2000 > 75 > 4 > 175-180
Information Processing Letters > 2000 > 76 > 1-2 > 83-90
Information Processing Letters > 2008 > 105 > 6 > 249-254
Information Processing Letters > 2009 > 109 > 20 > 1172-1176