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: "approximation schemes for steiner forest on planar graphs and graphs of bounded treewidth"
  Abstract: We give the first polynomial-time approximation scheme (PTAS) for the Steiner forest problem on planar graphs and, more generally, on graphs of bounded genus. As a first step, we show how to build a Steiner forest spanner for such graphs. The crux of the process is a clustering procedure called prize-collecting clustering that breaks down the input instance into separate subinstances which are easier to handle; moreover, the terminals in different subinstances are far from each other. Each subinstance has a relatively inexpensive Steiner tree connecting all its terminals, and the subinstances can be solved (almost) separately. Another building block is a PTAS for Steiner forest on graphs of bounded treewidth. Surprisingly, Steiner forest is NP-hard even on graphs of treewidth 3. Therefore, our PTAS for bounded treewidth graph needs a nontrivial combination of approximation arguments and dynamic programming on the tree decomposition. We further show that Steiner forest can be solved in polynomial time for series-parallel graphs (graphs of treewidth at most two) by a novel combination of dynamic programming and minimum cut computations, completing our thorough complexity study of Steiner forest in the range of bounded treewidth graphs, planar graphs, and bounded genus graphs.

Connected through hyperedge HE-1 (induced by source paper "tight bounds for planar strongly connected steiner subgraph with fixed number of terminals and extensions"):
  with members:
    - "fpt inapproximability of directed cut and connectivity problems"
    - "complexity of the steiner network problem with respect to the number of terminals"
    - "the parameterized complexity of finding point sets with hereditary properties"
    - "homomorphisms are a good basis for counting small subgraphs"
    - "parameterized approximation algorithms for directed steiner network problems"
    - "the graph motif problem parameterized by the structure of the input graph"
    - "on subexponential parameterized algorithms for steiner tree and directed subset tsp on planar graphs"
    - "on the parameterized complexity of red blue points separation"

Connected through hyperedge HE-2 (induced by source paper "travelling on graphs with small highway dimension"):
  with members:
    - "hierarchy of transportation network parameters and hardness results"
    - "the parameterized hardness of the k center problem in transportation networks"
    - "a 1 varepsilon embedding of low highway dimension graphs into bounded treewidth graphs"
    - "structural parameters tight bounds and approximation for k r center"
    - "beyond highway dimension small distance labels using tree skeletons"
    - "solving generalized maximum weight connected subgraph problem for network enrichment analysis"
    - "fixed parameter approximations for k center problems in low highway dimension graphs"
    - "the traveling salesman problem low dimensionality implies a polynomial time approximation scheme"

Connected through hyperedge HE-3 (induced by source paper "near linear time approximation schemes for steiner tree and forest in low dimensional spaces"):
  with members:
    - "greedy spanners are optimal in doubling metrics"
    - "the greedy spanner is existentially optimal"
    - "a ptas for the steiner forest problem in doubling metrics"
    - "the traveling salesman problem low dimensionality implies a polynomial time approximation scheme"
    - "a light metric spanner"
    - "a polynomial time approximation scheme for euclidean steiner forest"
    - "an efficient polynomial time approximation scheme for steiner forest in planar graphs"
    - "fast construction of nets in low dimensional metrics and their applications"

Connected through hyperedge HE-4 (induced by source paper "ptas for steiner tree on map graphs"):
  with members:
    - "polynomial time approximation scheme for minimum k cut in planar and minor free graphs"
    - "local search yields approximation schemes for k means and k median in euclidean and minor free metrics"
    - "simple ptas s for families of graphs excluding a minor"
    - "an efficient polynomial time approximation scheme for steiner forest in planar graphs"
    - "approximate tree decompositions of planar graphs in linear time"

Connected through hyperedge HE-5 (induced by source paper "node weighted network design in planar and minor closed families of graphs"):
  with members:
    - "improved approximation algorithms for budgeted node weighted steiner problems"
    - "spider covers for prize collecting network activation problem"
    - "an improved approximation algorithm for the minimum cost subset k connected subgraph problem"
    - "an o k 3 log n approximation algorithm for vertex connectivity survivable network design"

Connected through hyperedge HE-6 (induced by source paper "the densest k subgraph problem in b outerplanar graphs"):
  with members:
    - "crossing patterns in nonplanar road networks"

Connected through hyperedge HE-7 (induced by source paper "a ptas for subset tsp in minor free graphs"):
  with members:
    - "truly optimal euclidean spanners"
    - "greedy spanners are optimal in doubling metrics"
    - "on subexponential parameterized algorithms for steiner tree and directed subset tsp on planar graphs"
    - "minor free graphs have light spanners"
    - "the greedy spanner is existentially optimal"
    - "linear size distance preservers"
    - "graph minors for preserving terminal distances approximately lower and upper bounds"
    - "a light metric spanner"

Connected through hyperedge HE-8 (induced by source paper "efficient black box reductions for separable cost sharing"):
  with members:
    - "a characterization of undirected graphs admitting optimal cost shares"
    - "designing networks with good equilibria under uncertainty"
    - "greedy algorithms for steiner forest"
    - "resource buying games"
    - "strategic cooperation in cost sharing games"
    - "an o lognloglogn upper bound on the price of stability for undirected shapley network design games"
    - "an optimal bifactor approximation algorithm for the metric uncapacitated facility location problem"

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.DS(Data Structures and Algorithms)