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 highest deposition of Fe in soil could be due to its long-term use in the production of machine tools, paints, pigments and alloying in various industries of the study area that may contaminate soil (Yadav et al. 2013).
Category: