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: "equivalence checking on infinite state systems techniques and results"
  Abstract: The paper presents a selection of recently developed and/or used techniques for equivalence-checking on infinite-state systems, and an up-to-date overview of existing results (as of September 2004).

Connected through hyperedge HE-1 (induced by source paper "simulation problems over one counter nets"):
  with members:
    - "infinite state energy games"
    - "decidability of weak simulation on one counter nets"
    - "simulation over one counter nets is pspace complete"
    - "beyond language equivalence on visibly pushdown automata"

Connected through hyperedge HE-2 (induced by source paper "branching bisimilarity on normed bpa is exptime complete"):
  with members:
    - "dividing line between decidable pda s and undecidable ones"
    - "a polynomial time algorithm for deciding branching bisimilarity on totally normed bpa"
    - "branching bisimilarity of normed bpa processes is in nexptime"
    - "branching bisimilarity checking for prs"
    - "bisimilarity on basic process algebra is in 2 exptime an explicit proof"
    - "bpa bisimilarity is exptime hard"

Connected through hyperedge HE-3 (induced by source paper "a polynomial time algorithm for deciding branching bisimilarity on totally normed bpa"):
  with members:
    - "branching bisimilarity of normed bpa processes is in nexptime"

Connected through hyperedge HE-4 (induced by source paper "simulation over one counter nets is pspace complete"):
  with members:
    - "decidability of weak simulation on one counter nets"
    - "beyond language equivalence on visibly pushdown automata"

Connected through hyperedge HE-5 (induced by source paper "branching time model checking gap order constraint systems extended version"):
  with members:
    - "size change termination monotonicity constraints and ranking functions"

Connected through hyperedge HE-6 (induced by source paper "bpa bisimilarity is exptime hard"):
  with members:
    - "bisimilarity on basic process algebra is in 2 exptime an explicit proof"
    - "beyond language equivalence on visibly pushdown automata"
    - "decidability of higher order matching"
    - "model checking probabilistic timed automata with one or two clocks"
    - "the bisimulation problem for equational graphs of finite out degree"

Connected through hyperedge HE-7 (induced by source paper "bisimilarity of pushdown systems is nonelementary"):
  with members:
    - "bpa bisimilarity is exptime hard"
    - "the bisimulation problem for equational graphs of finite out degree"

Connected through hyperedge HE-8 (induced by source paper "reachability games on extended vector addition systems with states"):
  with members:
    - "forward analysis for wsts part ii complete wsts"
    - "forward analysis for wsts part i completions"

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)