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:Mutations in the dally locus encoding the Drosophila homolog of a human glycoprotein have been shown to result in numerous developmental defects, some of which are associated with alterations in dpp signaling (Haerry et al. 1997).
Category: