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: "normal order reduction grammars"
  Abstract: We present an algorithm which, for given $n$, generates an unambiguous regular tree grammar defining the set of combinatory logic terms, over the set $\{S,K\}$ of primitive combinators, requiring exactly $n$ normal-order reduction steps to normalize. As a consequence of Curry and Feys's standardization theorem, our reduction grammars form a complete syntactic characterization of normalizing combinatory logic terms. Using them, we provide a recursive method of constructing ordinary generating functions counting the number of $S K$-combinators reducing in $n$ normal-order reduction steps. Finally, we investigate the size of generated grammars, giving a primitive recursive upper bound.

Connected through hyperedge HE-1 (induced by source paper "combinatorics of explicit substitutions"):
  with members:
    - "counting environments and closures"
    - "combinatorics of lambda terms a natural approach"
    - "leftmost outermost beta reduction is invariant indeed"
    - "a natural counting of lambda terms"
    - "counting and generating terms in the binary lambda calculus extended version"
    - "modular complexity analysis for term rewriting"
    - "counting and generating lambda terms"
    - "on constructor rewrite systems and the lambda calculus"

Connected through hyperedge HE-2 (induced by source paper "on the enumeration of closures and environments with an application to random generation"):
  with members:
    - "combinatorics of explicit substitutions"
    - "leftmost outermost beta reduction is invariant indeed"
    - "a natural counting of lambda terms"
    - "counting and generating terms in the binary lambda calculus extended version"
    - "on constructor rewrite systems and the lambda calculus"
    - "smoothed analysis of algorithms why the simplex algorithm usually takes polynomial time"

Connected through hyperedge HE-3 (induced by source paper "towards the average case analysis of substitution resolution in lambda calculus"):
  with members:
    - "combinatorics of explicit substitutions"
    - "leftmost outermost beta reduction is invariant indeed"

Connected through hyperedge HE-4 (induced by source paper "on the likelihood of normalisation in combinatory logic"):
  with members:
    - "counting and generating terms in the binary lambda calculus extended version"

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)