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:Presence/absence screening for apicomplexans in scleractinian corals
Extraction of coral holobiont DNA utilized the Wizard (Promega) DNA preparation protocol (Thornhill et al. 2006b; Kemp et al. 2008).
Category: