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:…high mean concentration of Fe in leafy green plants was lower than the concentrations (140, 292.35 and 601.9 mg/kg) obtained by Brar et al. (2000) in India; Yadav et al. (2013) in India; and Al-Jaboobi et al. (2014) in Morocco for leafy green plants irrigated with groundwater, respectively.
Category: