(DIR) xkcd - A Webcomic of Romance, Sarcasm, Math and Language.
 (DIR) Floodgap Gopher Fun and Games
        
       xkcd - A Webcomic - Millennium Problems (2320)
        
       Image:
 (PNG) millennium_problems.png
        
       The hard part about opening a hole in the proof of the Poincaré
       conjecture is that Grigori Perelman will come out of retirement
       to try to fix it by drawing a loop around the hole and
       contracting it to a point.
        
       Comics reproduced from www.xkcd.com under license.
 (HTM) xkcd License (WWW)
 (HTM) xkcd Web Site (WWW)
        
       Previous:
 (DIR) xkcd - A Webcomic - Large Number Formats (2319)
       Next:
 (DIR) xkcd - A Webcomic - Low-Background Metal (2321)