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 form bisimulations for delimited control operators"
  Abstract: We define a notion of normal form bisimilarity for the untyped call-by-value lambda calculus extended with the delimited-control operators shift and reset. Normal form bisimilarities are simple, easy-to-use behavioral equivalences which relate terms without having to test them within all contexts (like contextual equivalence), or by applying them to function arguments (like applicative bisimilarity). We prove that the normal form bisimilarity for shift and reset is sound but not complete w.r.t. contextual equivalence and we define up-to techniques that aim at simplifying bisimulation proofs. Finally, we illustrate the simplicity of the techniques we develop by proving several equivalences on terms.

Connected through hyperedge HE-1 (induced by source paper "bisimulations for delimited control operators"):
  with members:
    - "proving soundness of extensional normal form bisimilarities"
    - "environmental bisimulations for delimited control operators with dynamic prompt generation"
    - "proving termination of evaluation for system f with control operators"
    - "environmental bisimulations for delimited control operators"
    - "applicative bisimulations for delimited control operators"
    - "an operational foundation for delimited continuations in the cps hierarchy"
    - "delimited continuations in natural language quantification and polarity sensitivity"

Connected through hyperedge HE-2 (induced by source paper "proving soundness of extensional normal form bisimilarities"):
  with members:
    - "environmental bisimulations for delimited control operators with dynamic prompt generation"
    - "an operational foundation for delimited continuations in the cps hierarchy"

Connected through hyperedge HE-3 (induced by source paper "environmental bisimulations for delimited control operators"):
  with members:
    - "applicative bisimulations for delimited control operators"
    - "an operational foundation for delimited continuations in the cps hierarchy"
    - "split 2 bisimilarity has a finite axiomatization over ccs with hennessy s merge"

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.PL(Programming Languages)