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 associations of rs2305480 with asthma-like symptoms in children at the age of 1, 2, 3, and 4 and the overall effects at all ages were analyzed using multiple imputation-based generalized estimating equation (MI-GEE) models (18, 19).
Category: