KD_Tree

http://en.wikipedia.org/wiki/Kd_tree

k_NN

http://saravananthirumuruganathan.wordpress.com/2010/05/17/a-detailed-introduction-to-k-nearest-neighbor-knn-algorithm/

http://simsearch.yury.name/tutorial.html

http://people.revoledu.com/kardi/tutorial/DecisionTree/how-decision-tree-algorithm-work.htm