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:In the study by Hickey et al. (2012), spikes were sampled from the field at the point of physiological
robinson et al.: genomic regions influencing root traits in barley 11 of 13
maturity, dried, grain threshed by hand, and stored at −20C to preserve grain dormancy before germination testing.
Category: