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:Moreno et al. (1991); Rojas et al. (2001) and Moreira et al. (2008) have previously shown more isoamyl acetate production in coinoculation of S. cerevisiae with a non-Saccharomyces in wine fermentations.
Category: