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: "some results on a b choosability"
  Abstract: A solution to a problem of Erd\H{o}s, Rubin and Taylor is obtained by showing that if a graph $G$ is $(a:b)$-choosable, and $c/d > a/b$, then $G$ is not necessarily $(c:d)$-choosable. Applying probabilistic methods, an upper bound for the $k^{th}$ choice number of a graph is given. We also prove that a directed graph with maximum outdegree $d$ and no odd directed cycle is $(k(d+1):k)$-choosable for every $k \geq 1$. Other results presented in this article are related to the strong choice number of graphs (a generalization of the strong chromatic number). We conclude with complexity analysis of some decision problems related to graph choosability.

Connected through hyperedge HE-1 (induced by source paper "frameworks for solving turing kernel lower bound problem and finding natural candidate problems in np intermediate"):
  with members:
    - "turing kernelization for finding long paths and cycles in restricted graph classes"
    - "abusing the tutte matrix an algebraic instance compression for the k set cycle problem"
    - "point line cover the easy kernel is essentially tight"
    - "kernelization lower bounds by cross composition"
    - "non existence of polynomial kernels for the test cover problem"
    - "kernelization of packing problems"
    - "clique cover and graph separation new incompressibility results"
    - "co nondeterminism in compositions a kernelization lower bound for a ramsey type problem"

Connected through hyperedge HE-2 (induced by source paper "choosability with limited number of colors"):
  with members:
    - "the complexity of planar graph choosability"

Connected through hyperedge HE-3 (induced by source paper "a survey on the computational complexity of colouring graphs with forbidden subgraphs"):
  with members:
    - "bounding the clique width of h free chordal graphs"
    - "three coloring graphs with no induced seven vertex path ii using a triangle"
    - "the coloring problem for p 5 p 5 free graphs and p 5 k p e free graphs is polynomial"
    - "bounding clique width via perfect graphs"
    - "clique width of graph classes defined by two forbidden induced subgraphs"
    - "narrowing the complexity gap for colouring c_s p_t free graphs"
    - "4 coloring p_6 free graphs with no induced 5 cycles"
    - "polynomial time algorithms for minimum weighted colorings of p_5 bar p _5 free graphs and related graph classes"

Connected through hyperedge HE-4 (induced by source paper "the star and biclique coloring and choosability problems"):
  with members:
    - "biclique colouring verification complexity and biclique colouring power graphs"
    - "hereditary biclique helly graphs recognition and maximal biclique enumeration"

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)