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:Also, HA can interact with various cellular receptors, including CD44, RHAMM, and LYVE-1, to promote angiogenesis [6], as well as the growth, invasion and metastasis of tumors [7-9].
Category: