Information Processing Letters
Information Processing Letters > 1997 > 64 > 2 > 83-86
Information Processing Letters > 2001 > 80 > 4 > 213-219
Information Processing Letters > 2009 > 109 > 21-22 > 1193-1196
Information Processing Letters > 2010 > 110 > 8-9 > 321-324
Information Processing Letters > 2010 > 110 > 20 > 849-853