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:subtilis, this protein forms a complex with SpoIIIAH (Q-AH) that is bifunctional: it contributes to FS engulfment and it forms a feeding channel that allows nutrients (and possibly regulatory signals) to be transferred from the MC to the FS during spore assembly (Broder and Pogliano, 2006; Camp and Losick, 2009; Doan et al., 2009; Higgins and Dworkin, 2012).
Category: