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: "study of citation networks in tribology research"
  Abstract: This study aims to study citation networks among publications on tribology using a new software tool called “CitNetExplorer”. Bibliographic records related to tribology research were retrieved from Web of Science. Three data sets have been analyzed: (1) Core publications of tribology research, (2) publications on nanotribology (a sub-discipline of tribology) and (3) publications of Bharat Bhushan (a top-contributor to nanotribology research). The study provides insights into citation relations among tribology publications. It demonstrates the potential of the CitNetExplorer and suggests possible improvements. It also shows how the CitNetExplorer can be used to analyze networks of publications in a specific research field.

Connected through hyperedge HE-1 (induced by source paper "detecting the historical roots of tribology research a bibliometric analysis"):
  with members:
    - "detecting the historical roots of research fields by reference publication year spectroscopy rpys"
    - "referenced publication years spectroscopy applied to imetrics scientometrics journal of informetrics and a relevant subset of jasist"

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)