human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge groups authors who co-authored the same paper.

Details of the hypergraph:
Center hyperedge (induced by source paper "The University of Lisbon at CLEF 2006 ad-hoc task"):
  Abstract: This paper reports the participation of the XLDB Group from the University of Lisbon in the CLEF 2006 ad-hoc monolingual and bilingual subtasks for Portuguese. We present our IR system, detail the query expansion strategy and the weighting scheme, describe the submitted runs and discuss the obtained results.

Includes members:
  Member "The University of Lisbon at GeoCLEF 2006":
    also connected through other hyperedges:
      (none)

Question: Please tell me which research area the co-authored paper (i.e., the source paper of the center hyperedge) belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Computer science