human: Given a node-centered hypergraph: <hypergraph>, where nodes represent authors and hyperedges represent groups of authors who co-authored the same paper.

Details of the hypergraph:
Center node: "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.

Connected through hyperedge HE-1 (induced by source paper "The University of Lisbon at GeoCLEF 2006"):
  with members:
    (none)

Question: Please tell me which research area the center author belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Computer science