human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "the diagonal problem for higher order recursion schemes is decidable"):
  Abstract: A non-deterministic recursion scheme recognizes a language of finite trees. This very expressive model can simulate, among others, higher-order pushdown automata with collapse. We show decidability of the diagonal problem for schemes. This result has several interesting consequences. In particular, it gives an algorithm that computes the downward closure of languages of words recognized by schemes. In turn, this has immediate application to separability problems and reachability analysis of concurrent systems.

Includes members:
  Member "on word and frontier languages of unsafe higher order grammars":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "intersection types for unboundedness problems")
  Member "unboundedness and downward closures of higher order pushdown automata":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "regular separability and intersection emptiness are independent problems")
  Member "ordered tree pushdown systems":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "intersection types for unboundedness problems")
  Member "an approach to computing downward closures":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "reachability in vector addition systems is primitive recursive in fixed dimension")
  Member "using models to model check recursive schemes":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "around finite second order coherence spaces")
  Member "a characterization for decidable separability by piecewise testable languages":
    also connected through other hyperedges:
      - Hyperedge HE-6 (induced by source paper "regular separability and intersection emptiness are independent problems")
  Member "finite automata for the sub and superword closure of cfls descriptional and computational complexity":
    also connected through other hyperedges:
      - Hyperedge HE-7 (induced by source paper "the ideal approach to computing closed subsets in well quasi orderings")
  Member "computing downward closures for stacked counter automata":
    also connected through other hyperedges:
      - Hyperedge HE-8 (induced by source paper "the ideal approach to computing closed subsets in well quasi orderings")

Question: Please tell me which class the source paper belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.FL(Formal Languages and Automata Theory)