human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "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).

Connected through hyperedge HE-1 (induced by source paper "bisimulation equivalence of first order grammars is ackermann complete"):
  with members:
    - "equivalence of pushdown automata via first order grammars"
    - "complexity hierarchies beyond elementary"
    - "branching bisimilarity checking for prs"
    - "complexity bounds for ordinal based termination"
    - "bpa bisimilarity is exptime hard"
    - "beyond language equivalence on visibly pushdown automata"
    - "the bisimulation problem for equational graphs of finite out degree"

Connected through hyperedge HE-2 (induced by source paper "deciding semantic finiteness of pushdown processes and first order grammars w r t bisimulation equivalence"):
  with members:
    - "complexity hierarchies beyond elementary"
    - "note on undecidability of bisimilarity for second order pushdown processes"
    - "bisimilarity of pushdown systems is nonelementary"
    - "the bisimulation problem for equational graphs of finite out degree"

Question: Please tell me which class the center node 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)