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 proof of the pumping lemma for context free languages through pushdown automata"
  Abstract: The pumping lemma for context-free languages is a result about pushdown automata which is strikingly similar to the well-known pumping lemma for regular languages. However, though the lemma for regular languages is simply proved by using the pigeonhole principle on deterministic automata, the lemma for pushdown automata is proven through an equivalence with context-free languages and through the more powerful Ogden's lemma. We present here a proof of the pumping lemma for context-free languages which relies on pushdown automata instead of context-free grammars.

Connected through hyperedge HE-1 (induced by source paper "the computational power of parsing expression grammars"):
  with members:
    - "recognising and generating terms using derivatives of parsing expression grammars"
    - "linear parsing expression grammars"
    - "parsing expression grammars made practical"
    - "a declarative extension of parsing expression grammars for recognizing most programming languages"
    - "fast flexible and declarative construction of abstract syntax trees with pegs"
    - "derivatives of parsing expression grammars"
    - "trx a formally verified parser interpreter"
    - "a new approach to formal language theory by kolmogorov complexity"

Connected through hyperedge HE-2 (induced by source paper "a stack vector routing protocol for automatic tunneling"):
  with members:
    - "on a class of stochastic multilayer networks"
    - "distributed exact shortest paths in sublinear time"
    - "near linear lower bounds for distributed distance computations even in sparse networks"
    - "path computation in multi layer multi domain networks a language theoretic approach"

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)