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:In addition, because liver can be effectively targeted by in vivo delivery of short RNAs, it represents a good model for the development of anticancer miRNA-based approaches of gene therapy as previously reported for other liver diseases (48, 49).
Category: