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: "a decidable characterization of locally testable tree languages"
  Abstract: A regular tree language L is locally testable if membership of a tree in L#N#depends only on the presence or absence of some fix set of neighborhoods in the#N#tree. In this paper we show that it is decidable whether a regular tree#N#language is locally testable. The decidability is shown for ranked trees and#N#for unranked unordered trees.

Connected through hyperedge HE-1 (induced by source paper "wreath products of distributive forest algebras"):
  with members:
    - "going higher in the first order quantifier alternation hierarchy on words"
    - "piecewise testable tree languages"
    - "an effective characterization of the alternation hierarchy in two variable logic"
    - "wreath products of forest algebras with applications to tree logics"
    - "tree languages defined in first order logic with one quantifier alternation"

Connected through hyperedge HE-2 (induced by source paper "deciding definability in fo2 h v on trees"):
  with members:
    - "piecewise testable tree languages"
    - "wreath products of forest algebras with applications to tree logics"
    - "tree languages defined in first order logic with one quantifier alternation"
    - "two way unary temporal logic over trees"

Connected through hyperedge HE-3 (induced by source paper "wreath products of forest algebras with applications to tree logics"):
  with members:
    - "piecewise testable tree languages"
    - "tree languages defined in first order logic with one quantifier alternation"
    - "two way unary temporal logic over trees"
    - "logics for unranked trees an overview"
    - "algebraic recognizability of regular tree languages"

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.FL(Formal Languages and Automata Theory)