In algebraic topology, a Postnikov square is a certain cohomology operation from a first cohomology group H¹ to a third cohomology group H³, introduced by Postnikov (1949). Eilenberg (1952) described a generalization taking classes in H^t to H^2t+1.

• Eilenberg, Samuel (1952), "Homotopy groups and algebraic homology theories", Proceedings of the International Congress of Mathematicians, Cambridge, Massachusetts, 1950, vol. 2, Providence, R.I.: Amer. Math. Soc., pp. 350–353, MR 0045388, archived from the original on 2011-08-20, retrieved 2011-04-08 PDF
• Kharshiladze, A.F. (2001) [1994], "Postnikov square", Encyclopedia of Mathematics, EMS Press
• Postnikov, M. M. (1949), "The classification of continuous mappings of a three-dimensional polyhedron into a simply connected polyhedron of arbitrary dimension", Doklady Akademii Nauk SSSR, New Series (in Russian), 64: 461–462, MR 0029173

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