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 set and collection lemma"
  Abstract: A set S is independent if no two vertices from S are adjacent. In this paper we prove that if F is a collection of maximum independent sets of a graph, then there is a matching from S-{intersection of all members of F} into {union of all members of F}-S, for every independent set S. Based on this finding we give alternative proofs for a number of well-known lemmata, as the "Maximum Stable Set Lemma" due to Claude Berge and the "Clique Collection Lemma" due to Andr\'as Hajnal.

Connected through hyperedge HE-1 (induced by source paper "on the critical difference of almost bipartite graphs"):
  with members:
    - "on the core of a unicyclic graph"
    - "vertices belonging to all critical independent sets of a graph"
    - "critical sets in bipartite graphs"
    - "a characterization of konig egervary graphs using a common property of all maximum matchings"

Connected through hyperedge HE-2 (induced by source paper "critical and maximum independent sets of a graph"):
  with members:
    - "on the power of simple reductions for the maximum independent set problem"
    - "on the core of a unicyclic graph"
    - "on the intersection of all critical sets of a unicyclic graph"
    - "vertices belonging to all critical independent sets of a graph"
    - "on the structure of the minimum critical independent set of a graph"
    - "critical sets in bipartite graphs"

Connected through hyperedge HE-3 (induced by source paper "monotonic properties of collections of maximum independent sets of a graph"):
  with members:
    - "on the core of a unicyclic graph"
    - "on the intersection of all critical sets of a unicyclic graph"
    - "vertices belonging to all critical independent sets of a graph"
    - "on the structure of the minimum critical independent set of a graph"
    - "critical sets in bipartite graphs"

Connected through hyperedge HE-4 (induced by source paper "on konig egervary collections of maximum critical independent sets"):
  with members:
    - "critical and maximum independent sets of a graph"
    - "monotonic properties of collections of maximum independent sets of a graph"
    - "critical independent sets of a graph"
    - "vertices belonging to all critical independent sets of a graph"

Connected through hyperedge HE-5 (induced by source paper "critical independent sets of a graph"):
  with members:
    - "vertices belonging to all critical independent sets of a graph"
    - "on the structure of the minimum critical independent set of a graph"
    - "critical sets in bipartite graphs"

Connected through hyperedge HE-6 (induced by source paper "on the intersection of all critical sets of a unicyclic graph"):
  with members:
    - "on the core of a unicyclic graph"
    - "vertices belonging to all critical independent sets of a graph"
    - "on the structure of the minimum critical independent set of a graph"
    - "critical sets in bipartite graphs"

Connected through hyperedge HE-7 (induced by source paper "critical sets in bipartite graphs"):
  with members:
    - "vertices belonging to all critical independent sets of a graph"

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.DM(Discrete Mathematics)