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[[FILE:SamuelBakQuiteClear.jpg|border|right|thumb|link=http://chgs.elevator.umn.edu/asset/viewAsset/57f3b6787d58ae5f74bf8ba9#57f3b6d77d58ae5574bf8bcb| [[:Category:Samuel Bak|Samuel Bak]], Quite Clear <ref>[http://chgs.elevator.umn.edu/asset/viewAsset/57f3b6787d58ae5f74bf8ba9#57f3b6d77d58ae5574bf8bcb Chess in the Art of Samuel Bak], [http://chgs.elevator.umn.edu/ Center for Holocaust & Genocide Studies], [https://en.wikipedia.org/wiki/University_of_Minnesota [University of Minnesota]]</ref> <ref>The mountain in the background looks like [https://en.wikipedia.org/wiki/Torghatten Torghatten] near [https://en.wikipedia.org/wiki/Br%C3%B8nn%C3%B8ysund Brønnøysund]</ref> ]]

[[Dan Heisman]] <ref>[[Dan Heisman]] ('''1990, 1999, 2010, 2015''').''[http://www.danheisman.com/elements-of-positional-evaluation.html The Positional Elements of ChessPositional Evaluation]''. Russell Enterprises</ref> represents an attempt at mathematical abstraction applied to chess, introducing seven concepts as fundamental in analyzing a chess position: mobility, flexibility, vulnerability, [[Center Control|center control]], piece coordination, time and speed. Heisman applies two [https://en.wikipedia.org/wiki/Dichotomy dichotomies]: ''actual'' versus ''potential'' and ''local'' versus ''global'':