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:…0.07– 0.97, 0.45–4.1, 7.4–8.9, 2.97–18.92 and 12–35 mg/kg) in leafy green plants from Malaysia, Sri Lanka, China, Kathmandu, India and Turkey, respectively (Aweng et al. 2011; Kananke et al. 2014; Zhuang et al. 2009; Shakya and Khwaounjoo 2013; Yadav et al. 2013; Türkdoğan et al. 2002).
Category: