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: "digital repository of mathematical formulae"
  Abstract: The purpose of the NIST Digital Repository of Mathematical Formulae (DRMF) is to create a digital compendium of mathematical formulae for orthogonal polynomials and special functions (OPSF) and of associated mathematical data. The DRMF addresses needs of working mathematicians, physicists and engineers: providing a platform for publication and interaction with OPSF formulae on the web. Using MediaWiki extensions and other existing technology (such as software and macro collections developed for the NIST Digital Library of Mathematical Functions), the DRMF acts as an interactive web domain for OPSF formulae. Whereas Wikipedia and other web authoring tools manifest notions or descriptions as first class objects, the DRMF does that with mathematical formulae. See http://gw32.iu.xsede.org/index.php/Main_Page .

Connected through hyperedge HE-1 (induced by source paper "fungrim a symbolic library for special functions"):
  with members:
    - "arb efficient arbitrary precision midpoint radius interval arithmetic"

Connected through hyperedge HE-2 (induced by source paper "semantic preserving bijective mappings for expressions involving special functions between computer algebra systems and document preparation systems"):
  with members:
    - "improving the representation and conversion of mathematical formulae by considering their textual context"
    - "branch cuts in maple 17"

Connected through hyperedge HE-3 (induced by source paper "improving the representation and conversion of mathematical formulae by considering their textual context"):
  with members:
    - "vmext a visualization tool for mathematical expression trees"
    - "interoperability in the opendreamkit project the math in the middle approach"
    - "growing the digital repository of mathematical formulae with generic latex sources"
    - "mathoid robust scalable fast and accessible math rendering for wikipedia"
    - "branch cuts in maple 17"
    - "rted a robust algorithm for the tree edit distance"

Connected through hyperedge HE-4 (induced by source paper "vmext a visualization tool for mathematical expression trees"):
  with members:
    - "growing the digital repository of mathematical formulae with generic latex sources"
    - "strategies for parallel markup"
    - "a survey on retrieval of mathematical knowledge"
    - "mathoid robust scalable fast and accessible math rendering for wikipedia"

Connected through hyperedge HE-5 (induced by source paper "math aware search engines physics applications and overview"):
  with members:
    - "combining text and formula queries in math information retrieval evaluation of query results merging strategies"
    - "the tangent search engine improved similarity metrics and scalability for math formula search"
    - "which one is better presentation based or content based math search"
    - "ontomath pro ontology a linked data hub for mathematics"
    - "mathematical knowledge management is needed"

Connected through hyperedge HE-6 (induced by source paper "growing the digital repository of mathematical formulae with generic latex sources"):
  with members:
    - "mathematical language processing project"
    - "which one is better presentation based or content based math search"
    - "mathoid robust scalable fast and accessible math rendering for wikipedia"

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.DL(Digital Libraries)