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a Dutch computer chess expert, who published and maintained interesting chess <ref>[https://web.archive.org/web/20010408203313/http://www.xs4all.nl/~verhelst/chess/links.html Paul Verhelst's chess pages] ([https://en.wikipedia.org/wiki/Wayback_Machine Wayback Machine], April 08, 2001)</ref> and [[Programming|chess programming]] sites <ref>[https://web.archive.org/web/20010405091155/http://www.xs4all.nl/~verhelst/chess/programming.html Paul Verhelst's chess programming pages] ([https://en.wikipedia.org/wiki/Wayback_Machine Wayback Machine], April 05, 2001)</ref>.[[Ed Schroder|Ed Schröder]] once mentioned the [[0x88]] [[0x88#SquareRelations|square difference]] lookup as Paul Verhelst way <ref>[http://www.talkchess.com/forum3/viewtopic.php?f=7&t=59315&start=11 Re: futility pruning] by [[Ed Schroder|Ed Schröder]], [[CCC]], March 11, 2016</ref>,which was used and described by [[Paul Wiereyn]] <ref>[[Paul Wiereyn]] ('''1985'''). ''Inventive Problem Solving''. [[ICGA Journal#8_4|ICCA Journal, Vol. 8, No. 4]]</ref> and , according to [[David Kittinger]], was originally attributed to [[Mikhail Botvinnik]] <ref>[http://www.talkchess.com/forum/viewtopic.php?topic_view=threads&p=462693&t=43447 Re: Hello all] by [[David Kittinger|Dave Kittinger]], [[CCC]], April 26, 2012</ref>.