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:However, no previous studies have looked into lesions caused by CY and role of Vit E and Se in alleviating the harmful effects of CY in broiler chicks except one (Sharaf et al., 2009), which has dealt with hematological alterations and their attenuation by Vit E and Se.
Category: