Update: PriorityQueue: Addition of the related publication by Atkinson
// Priority queue //
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//The priority queue for concepts and tasks
+//Related publication: Atkinson, M. D., Sack, J. R., Santoro, N., & Strothotte, T. (1986). Min-max heaps and generalized priority queues. Communications of the ACM, 29(10), 996-1000.
//Ported from https://github.com/quxiaofeng/python-stl/blob/master/meshlab/MeshLabSrc_AllInc_v132/meshlab/src/plugins_experimental/edit_ocme/src/cache/old/mmheap.h
//References//
