{ "items" : [
    { "id" : "http://dbpedia.org/resource/Hilbert's_nineteenth_problem"
      "properties" : {
        "http://www.w3.org/2000/01/rdf-schema#comment" : [ "Hilbert's nineteenth problem is one of the 23 Hilbert problems, set out in a celebrated list compiled in 1900 by David Hilbert. It asks whether the solutions of regular problems in the calculus of variations are always analytic. Informally, and perhaps less directly, since Hilbert's concept of a \"regular variational problem\" identifies precisely a variational problem whose Euler–Lagrange equation is an elliptic partial differential equation with analytic coefficients."] } } }
