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: "tree languages defined in first order logic with one quantifier alternation"
  Abstract: We study tree languages that can be defined in \Delta_2 . These are tree#N#languages definable by a first-order formula whose quantifier prefix is forall#N#exists, and simultaneously by a first-order formula whose quantifier prefix is#N#. For the quantifier free part we consider two signatures, either the#N#descendant relation alone or together with the lexicographical order relation#N#on nodes. We provide an effective characterization of tree and forest languages#N#definable in \Delta_2 . This characterization is in terms of algebraic#N#equations. Over words, the class of word languages definable in \Delta_2 forms#N#a robust class, which was given an effective algebraic characterization by Pin#N#and Weil.

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"
    - "a decidable characterization of locally testable tree languages"

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"
    - "a decidable characterization of locally testable tree languages"
    - "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"
    - "a decidable characterization of locally testable tree languages"
    - "two way unary temporal logic over trees"
    - "logics for unranked trees an overview"
    - "algebraic recognizability of regular tree languages"

Connected through hyperedge HE-4 (induced by source paper "a decidable characterization of locally testable tree languages"):
  with members:
    - "piecewise testable tree languages"
    - "two way unary temporal logic over trees"
    - "algebraic recognizability of regular tree languages"

Connected through hyperedge HE-5 (induced by source paper "fragments of first order logic over infinite words"):
  with members:
    - "piecewise testable tree languages"
    - "two way unary temporal logic over trees"
    - "logic meets algebra the case of regular languages"
    - "algebraic recognizability of languages"

Connected through hyperedge HE-6 (induced by source paper "algebraic characterization of logically defined tree languages"):
  with members:
    - "piecewise testable tree languages"
    - "two way unary temporal logic over trees"
    - "algebraic recognizability of languages"
    - "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)