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:The spike protein of CoVs is a membrane glycoprotein that contains important antigenic determinants and neutralizing epitopes and plays a key role in mediating the entry of the CoVs into host cells through receptor binding and membrane fusion (Cruz et al, 2008; Sun et al, 2008; Li, 2015).
Category: