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: "finding vertex surjective graph homomorphisms"
  Abstract: The Surjective Homomorphism problem is to test whether a given graph G called the guest graph allows a vertex-surjective homomorphism to some other given graph H called the host graph. The bijective and injective homomorphism problems can be formulated in terms of spanning subgraphs and subgraphs, and as such their computational complexity has been extensively studied. What about the surjective variant? Because this problem is NP-complete in general, we restrict the guest and the host graph to belong to graph classes G and H, respectively. We determine to what extent a certain choice of G and H influences its computational complexity. We observe that the problem is polynomial-time solvable if H is the class of paths, whereas it is NP-complete if G is the class of paths. Moreover, we show that the problem is even NP-complete on many other elementary graph classes, namely linear forests, unions of complete graphs, cographs, proper interval graphs, split graphs and trees of pathwidth at most 2. In contrast, we prove that the problem is fixed-parameter tractable in k if G is the class of trees and H is the class of trees with at most k leaves, or if G and H are equal to the class of graphs with vertex cover number at most k.

Connected through hyperedge HE-1 (induced by source paper "the complexity of boolean surjective general valued csps"):
  with members:
    - "a dichotomy theorem for nonuniform csps"
    - "the proof of csp dichotomy conjecture"
    - "the complexity of finite valued csps"
    - "a galois connection for weighted relational clones of infinite size"
    - "algebraic properties of valued constraint satisfaction problem"
    - "the complexity of general valued csps"
    - "an algebraic hardness criterion for surjective constraint satisfaction"
    - "an algebraic theory of complexity for discrete optimization"

Connected through hyperedge HE-2 (induced by source paper "the complexity of counting surjective homomorphisms and compactions"):
  with members:
    - "homomorphisms are a good basis for counting small subgraphs"
    - "surjective h colouring new hardness results"
    - "homomorphisms are indeed a good basis for counting three fixed template dichotomy theorems for the price of one"
    - "note on the complexity of counting surjective homomorphisms and compactions"
    - "counting homomorphisms to square free graphs modulo 2"
    - "the complexity of surjective homomorphism problems a survey"

Connected through hyperedge HE-3 (induced by source paper "surjective h colouring new hardness results"):
  with members:
    - "the complexity of surjective homomorphism problems a survey"

Connected through hyperedge HE-4 (induced by source paper "on retracts absolute retracts and folds in cographs"):
  with members:
    - "cleaning interval graphs"
    - "an effective dichotomy for the counting constraint satisfaction problem"
    - "split decomposition and graph labelled trees characterizations and fully dynamic algorithms for totally decomposable graphs"
    - "a complexity dichotomy for partition functions with mixed signs"

Connected through hyperedge HE-5 (induced by source paper "the complexity of surjective homomorphism problems a survey"):
  with members:
    - "approximation for maximum surjective constraint satisfaction problems"
    - "the complexity of rooted phylogeny problems"
    - "the complexity of global cardinality constraints"
    - "the stubborn problem is stubborn no more a polynomial algorithm for 3 compatible colouring and the stubborn list partition problem"
    - "orthomodular lattices foulis semigroups and dagger kernel categories"
    - "the approximability of three valued max csp"

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)