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: "extending search facilities via bibliometric enhanced stratagems"
  Abstract: The paper introduces simple bibliometric-enhanced search facilities which are derived from the famous stratagems by Bates. Moves, tactics and stratagems are revisited from a Digital Library perspective. The potential of extended versions of "journal run" or "citation search" for interactive information retrieval is outlined. The authors elaborate on the future implementation and evaluation of new bibliometric-enhanced search services.

Connected through hyperedge HE-1 (induced by source paper "analysis of search stratagem utilisation"):
  with members:
    - "investigating exploratory search activities based on the stratagem level in digital libraries"
    - "contextualised browsing in a digital library s living lab"
    - "analysis of footnote chasing and citation searching in an academic search engine"
    - "a complete year of user retrieval sessions in a social sciences academic search engine"
    - "a usefulness based approach for measuring the local and global effect of iir services"
    - "scientometrics and information retrieval weak links revitalized"
    - "science models as value added services for scholarly information systems"

Connected through hyperedge HE-2 (induced by source paper "contextualised browsing in a digital library s living lab"):
  with members:
    - "data requirements for evaluation of personalization of information retrieval a position paper"
    - "investigating exploratory search activities based on the stratagem level in digital libraries"
    - "a complete year of user retrieval sessions in a social sciences academic search engine"
    - "a usefulness based approach for measuring the local and global effect of iir services"
    - "cross concordances terminology mapping and its effectiveness for information retrieval"

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)