{ "items" : [
    { "id" : "http://dbpedia.org/resource/Postnikov_square"
      "properties" : {
        "http://www.w3.org/2000/01/rdf-schema#comment" : [ "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 Ht to H2t+1."] } } }
