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 reasons for excluding the toxic endpoints of necrotizing enterocolitis and ROP are that necrotizing enterocolitis and other GI toxicities were proven not to be associated with INDO dose or concentrations [24], and the association of ROP [20] was speculative given the secondary analysis and different treatment populations a priori for different dosing levels used to analyze that aspect of the study [11].
Category: