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:tems in (Poon and Domingos, 2008; Haghighi and Klein, 2009; Raghunathan et al., 2010), with the best results so far obtained by the deterministic sieve system of Lee at al.
Category: