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:Five-microliter yeast cells were spotted onto the interaction selection media (synthetic complete agar-Leu-Trp-His-Ala with 1.5 mM 3-amino-1,2,4-aminotriazole) to score growth as an indicator of protein‚Äìprotein interaction (Lee et al., 2007).
Category: