Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:wind sector: CD 1⁄4 0:130 and CDa 1⁄4 0:132) and they are very close to the values found in literature (e.g. Amiro 1990; Kerzenmacher and Gardiner 1998; Pinard and Wilson 2001).
Category: