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:This result is in agreement with previous studies working on carotenoid contents in macroalgae (Hanelt et al. 1997; Schofield et al. 1998; Harker et al. 1999).
Category: