Looking for a cool gift for someone mathematically inclined? An unusual, conversation-generating token of appreciation? The World Wide Web offers a number of intriguing possibilities–if you know where to stop and shop.
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A little ad in a mathematics newsletter recently alerted me to the Math Hatter Web site (http://www.mathhatter.com/), which offers “mathematical softwear for your head.” It specializes in winter headgear: Klein bottle caps and Möbius earbands, each available in several different colors (one side fits all).