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:, 2011) or enteric polymers such as hydroxypropyl methylcellulose phthalate (HPMCP) (Miyazaki et al., 2011) and hydroxypropyl methylcellulose acetate succinate (HPMCAS) (Friesen et al.
Category: