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:R intergenic region. pTH1960 was introduced into RmP110, RmP1710 and RmP1712 through triparental conjugation with the E. coli helper strain MT616 (pRK600) (Finan et al., 1986).
Category: