{ "items" : [
    { "id" : "http://dbpedia.org/resource/Pseudo-differential_operator"
      "properties" : {
        "http://www.w3.org/2000/01/rdf-schema#comment" : [ "In mathematical analysis a pseudo-differential operator  is an extension of the concept of differential operator. Pseudo-differential operators are used extensively in the theory of partial differential equations and quantum field theory."] } } }
