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:For amplification of over 500 bp of rpoB, primers (rpobF, rpoBR, rpoBF2 and rpoBR2) and PCR cycling conditions described by Rajaniemi et al. (2005) were used.
Category: