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 variables with few occurrences in conjunctive normal forms"
  Abstract: We consider the question of the existence of variables with few occurrences in boolean conjunctive normal forms (clause-sets). Let µvd(F) for a clause-set F denote the minimal variable-degree, the minimum of the number of occurrences of variables. Our main result is an upper bound µvd(F) = nM(σ(F)) = σ(F) + 1 + log2(σ(F)) for lean clause-sets F in dependency on the surplus σ(F). Lean clause-sets, defined as having no non-trivial autarkies, generalise minimally unsatisfiable clause-sets. For the surplus we have σ(F) = σ(F) = c(F)-n(F), using the deficiency σ(F) of clause-sets, the difference between the number of clauses and the number of variables. nM(k) is the k-th "non-Mersenne" number, skipping in the sequence of natural numbers all numbers of the form 2n-1. As an application of the upper bound we obtain that clausesets F violating µvd(F) = nM(σ(F)) must have a non-trivial autarky (so clauses can be removed satisfiability-equivalently by an assignment satisfying some clauses and not touching the other clauses). It is open whether such an autarky can be found in polynomial time.

Connected through hyperedge HE-1 (induced by source paper "minimal unsatisfiability and deficiency recent developments"):
  with members:
    - "unsatisfiable hitting clause sets with three more clauses than variables"
    - "parameters for minimal unsatisfiability smarandache primitive numbers and full clauses"

Connected through hyperedge HE-2 (induced by source paper "unsatisfiable hitting clause sets with three more clauses than variables"):
  with members:
    - "parameters for minimal unsatisfiability smarandache primitive numbers and full clauses"
    - "on davis putnam reductions for minimally unsatisfiable clause sets"

Connected through hyperedge HE-3 (induced by source paper "parameters for minimal unsatisfiability smarandache primitive numbers and full clauses"):
  with members:
    - "on davis putnam reductions for minimally unsatisfiable clause sets"

Connected through hyperedge HE-4 (induced by source paper "on davis putnam reductions for minimally unsatisfiable clause sets"):
  with members:
    - "constraint satisfaction problems in clausal form"

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)