By Collins KS2
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By Tsokos, K. A.
By Angela Fox Dunn
By Greg N. Frederickson (Purdue University, Indiana)
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By Patrick Bossert
By Marcus Du Sautoy
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By AIIA, Times Mind Games
By Hard Charlotte
By Alex Bellos, Ben Lyttleton, Spike Gerrell
By Martin Gardner, Dana Richards
By Gould
By Gould, Wayne
By Holt, Michael, Ridout, Ronald
By Ben Fogle
By Martin, Guy
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By Rob Eastaway
By Karl Fulves
By Daniel Grieser
By Amir D. Azcel
By Martin Gardner
By Graham Farmelo
By Beasley, Georgie
By Donaldson, Julia, Pichon, Liz
By Lewis Carroll, Martin Gardner, Sir John Tenniel