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 results of the 2-year illicit drug use outcomes from the full Preventure Trial (Waves 1 and 2 combined) were then reported by Conrod et al. (2010), showing that the intervention was associated with a greater likelihood of surviving 2 years without taking up drug use.
Category: