human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent groups of papers sharing a common citing paper.

Details of the hypergraph:
Center node: "Approximation from shift-invariant subspaces of L"
  Abstract: A complete characterization is given of closed shift-invariant subspaces of L 2 (IR d ) which provide a specified approximation order. When such a space is principal (i.e., generated by a single function), then this characterization is in terms of the Fourier transform of the generator. As a special case, we obtain the classical Strang-Fix conditions, but without requiring the generating function to decay at infinity. The approximation order of a general closed shift-invariant space is shown to be already realized by a specifiable principal subspace.

Connected through hyperedge HE-1 (induced by source paper "Radial basis function approximation: from gridded centers to scattered centers"):
  with members:
    - "Radial Basis Functions: L p -approximation orders with scattered centres"
    - "APPROXIMATION IN L p (R d FROM SPACES SPANNED BY THE PERTURBED INTEGER TRANSLATES OF"
    - "Negative observations concerning approximations from spaces generated by scattered shifts of functions vanishing at 1"

Connected through hyperedge HE-2 (induced by source paper "Negative observations concerning approximations from spaces generated by scattered shifts of functions vanishing at 1"):
  with members:
    - "Radial basis function approximation: from gridded centers to scattered centers"

Question: Please tell me which class the center node belongs to. The 7 classes are: Neural_Networks, Reinforcement_Learning, Probabilistic_Methods, Theory, Genetic_Algorithms, Case_Based, Rule_Learning. Directly output the class name.

gpt: Neural_Networks