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 "bisimulation equivalence of first order grammars"):
  Abstract: A decidability proof for bisimulation equivalence of first-order grammars (finite sets of labelled rules for rewriting roots of first-order terms) is presented. The equivalence generalizes the DPDA (deterministic pushdown automata) equivalence, and the result corresponds to the result achieved by Senizergues (1998, 2005) in the framework of equational graphs, or of PDA with restricted epsilon-steps. The framework of classical first-order terms seems particularly useful for providing a proof that should be understandable for a wider audience. We also discuss an extension to branching bisimilarity, announced by Fu and Yin (2014).

Includes members:
  Member "complexity hierarchies beyond elementary":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "the ideal approach to computing closed subsets in well quasi orderings")
  Member "dividing line between decidable pda s and undecidable ones":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "branching bisimilarity on normed bpa is exptime complete")
  Member "branching bisimilarity checking for prs":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "bisimulation equivalence of first order grammars is ackermann complete")
  Member "bisimilarity on basic process algebra is in 2 exptime an explicit proof":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "branching bisimilarity of normed bpa processes as a rational monoid")
  Member "bpa bisimilarity is exptime hard":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "bisimulation equivalence of first order grammars is ackermann complete")
  Member "on the complexity of the equivalence problem for probabilistic automata":
    also connected through other hyperedges:
      - Hyperedge HE-6 (induced by source paper "relations on words")
  Member "the bisimulation problem for equational graphs of finite out degree":
    also connected through other hyperedges:
      - Hyperedge HE-7 (induced by source paper "bisimulation equivalence of first order grammars is ackermann complete")

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.LO(Logic in Computer Science)