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 "wreath products of distributive forest algebras"):
  Abstract: It is an open problem whether definability in Propositional Dynamic Logic (PDL) on forests is decidable. Based on an algebraic characterization by Bojanczyk, et. al., (2012) in terms of forest algebras, Straubing (2013) described an approach to PDL based on a k-fold iterated distributive law. A proof that all languages satisfying such a k-fold iterated distributive law are in PDL would settle decidability of PDL. We solve this problem in the case k = 2: All languages recognized by forest algebras satisfying a 2-fold iterated distributive law are in PDL. Furthermore, we show that this class is decidable. This provides a novel nontrivial decidable subclass of PDL, and demonstrates the viability of the proposed approach to deciding PDL in general.

Includes members:
  Member "going higher in the first order quantifier alternation hierarchy on words":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "on all things star free")
  Member "piecewise testable tree languages":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "partially ordered automata and piecewise testability")
  Member "an effective characterization of the alternation hierarchy in two variable logic":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "finite degree predicates and two variable first order logic")
  Member "wreath products of forest algebras with applications to tree logics":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "first order tree to tree functions")
  Member "a decidable characterization of locally testable tree languages":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "deciding definability in fo2 h v on trees")
  Member "tree languages defined in first order logic with one quantifier alternation":
    also connected through other hyperedges:
      - Hyperedge HE-6 (induced by source paper "deciding definability in fo2 h v on trees")

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.FL(Formal Languages and Automata Theory)