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:‚Ä¶of the common 59 leader sequence to the different 39 body segments present in arterivirus and coronavirus sg mRNAs (previously reviewed by e.g. Sawicki & Sawicki, 1995, 2005; van der Most & Spaan, 1995; Lai & Cavanagh, 1997; Brian & Spaan, 1997; Snijder & Meulenberg, 1998; Lai & Holmes, 2001).
Category: