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: "growth in the number of references in engineering journal papers during the 1972 2013 period"
  Abstract: The number of references per paper, perhaps the best single index of a journal's scholarliness, has been studied in different disciplines and periods. In this paper we present a four decade study of eight engineering journals. A data set of over 70,000 references was generated after automatic data gathering and manual inspection for errors. Results show a significant increase in the number of references per paper, the average rises from 8 in 1972 to 25 in 2013. This growth presents an acceleration around the year 2000, consistent with a much easier access to search engines and documents produced by the generalization of the Internet.

Connected through hyperedge HE-1 (induced by source paper "over optimization of academic publishing metrics observing goodhart s law in action"):
  with members:
    - "h index manipulation by merging articles"
    - "the google scholar experiment how to index false papers and manipulate bibliometric indicators"
    - "weighted citation an indicator of an article s prestige"
    - "graphlab a new framework for parallel machine learning"
    - "towards a new crown indicator an empirical analysis"

Connected through hyperedge HE-2 (induced by source paper "citation score normalized by cited references csncr the introduction of a new citation impact indicator"):
  with members:
    - "a review of theory and practice in scientometrics"
    - "a review of the literature on citation impact indicators"
    - "investigation of partition cells as a structural basis suitable for assessments of individual scientists"
    - "methods for the generation of normalized citation impact scores in bibliometrics which method best reflects the judgements of experts"
    - "on the causes of subject specific citation rates in web of science"
    - "universality of scholarly impact metrics"
    - "citation analysis may severely underestimate the impact of clinical research as compared to basic research"
    - "a systematic empirical comparison of different approaches for normalizing citation impact indicators"

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)