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: "on the parameterized intractability of monadic second order logic"
  Abstract: One of Courcelle's celebrated results states that if C is a class of graphs#N#of bounded tree-width, then model-checking for monadic second order logic#N#(MSO_2) is fixed-parameter tractable (fpt) on C by linear time parameterized#N#algorithms, where the parameter is the tree-width plus the size of the formula.#N#An immediate question is whether this is best possible or whether the result#N#can be extended to classes of unbounded tree-width. In this paper we show that#N#in terms of tree-width, the theorem cannot be extended much further. More#N#specifically, we show that if C is a class of graphs which is closed under#N#colourings and satisfies certain constructibility conditions and is such that#N#the tree-width of C is not bounded by \log^{84} n then MSO_2-model checking is#N#not fpt unless SAT can be solved in sub-exponential time. If the tree-width of#N#C is not poly-logarithmically bounded, then MSO_2-model checking is not fpt#N#unless all problems in the polynomial-time hierarchy can be solved in#N#sub-exponential time.

Connected through hyperedge HE-1 (induced by source paper "model checking lower bounds for simple graphs"):
  with members:
    - "problems parameterized by treewidth tractable in single exponential time a logical approach"
    - "deciding first order properties of locally tree decomposable structures"

Connected through hyperedge HE-2 (induced by source paper "subgraphs satisfying mso properties on z topologically orderable digraphs"):
  with members:
    - "digraph complexity measures and applications in formal language theory"
    - "lower bounds for the complexity of monadic second order logic"
    - "are there any good digraph width measures"

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)