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:Gestational age was assessed by mothers’ report of their last menstrual period (87 newborns), early ultrasound dating (two newborns) and New Ballard Score examination (six newborns).(2) Anthropometric measurements of the infants were taken two hours after delivery by nurses previously trained.
Category: