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 fact, a decrease of ROS production in AS-30D cells by the potent uncoupler CCCP, both in the presence and absence of arachidonic acid, was described in our previous publication (Dymkowska et al., 2006).
Category: