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: "a spatial scientometric analysis of the publication output of cities worldwide"
  Abstract: In tandem with the rapid globalisation of science, spatial scientometrics has become an important research sub-field in scientometric studies. Recently, numerous spatial scientometric contributions have focused on the examination of cities' scientific output by using various scientometric indicators. In this paper, I analyse cities' scientific output worldwide in terms of the number of journal articles indexed by the Scopus database, in the period from 1986 to 2015. Furthermore, I examine which countries are the most important collaborators of cities. Finally, I identify the most productive disciplines in each city. I use GPS Visualizer to illustrate the scientometric data of nearly 2,200 cities on maps. Results show that cities with the highest scientific output are mostly located in developed countries and China. Between 1986 and 2015, the greatest number of scientific articles were created in Beijing. The international hegemony of the United States in science has been described by many studies, and is also reinforced by the fact that the United States is the most important collaborator to more than 75 percent of all cities. Medicine is the most productive discipline in two-thirds of cities. Furthermore, cities having the highest scientific output in specific disciplines show well-defined geographical patterns.

Connected through hyperedge HE-1 (induced by source paper "on the challenges ahead of spatial scientometrics focusing on the city level"):
  with members:
    - "the geography of references in elite articles which countries contribute to the archives of knowledge"
    - "exploring the position of cities in global corporate research and development a bibliometric analysis by two different geographical approaches"
    - "concentration of research funding leads to decreasing marginal returns"
    - "a methodology to compute the territorial productivity of scientists the case of italy"
    - "a new bibliometric approach to assess the scientific specialization of regions"
    - "the european union china and the united states in the top 1 and top 10 layers of most frequently cited publications competition and collaborations"
    - "mapping excellence in the geography of science an approach based on scopus data"
    - "the detection of hot regions in the geography of science a visualization approach by using density maps"

Connected through hyperedge HE-2 (induced by source paper "factors influencing cities publishing efficiency"):
  with members:
    - "the relationship among research productivity research collaboration and their determinants"
    - "the sum of it all revealing collaboration patterns by combining authorship and acknowledgements"
    - "the journal coverage of web of science and scopus a comparative analysis"
    - "evaluating university research same performance indicator different rankings"
    - "the european union china and the united states in the top 1 and top 10 layers of most frequently cited publications competition and collaborations"
    - "international scientific collaboration of china collaborating countries institutions and individuals"
    - "mapping excellence in the geography of science an approach based on scopus data"
    - "the detection of hot regions in the geography of science a visualization approach by using density maps"

Connected through hyperedge HE-3 (induced by source paper "missing author address information in web of science an explorative study"):
  with members:
    - "book reviews in academic journals patterns and dynamics"
    - "funding acknowledgment analysis queries and caveats"
    - "constructing bibliometric networks a comparison between full and fractional counting"
    - "a new methodology for constructing a publication level classification system of science"
    - "globalisation of science in kilometres"

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)