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:Similar reductions in crested wheatgrass cover as a result of herbicide applications have been demonstrated in grasslands without patch burn grazing (Bakker et al., 1997; Hansen and Wilson, 2006; Wilson and Gerry, 1995; Wilson and Partel, 2003).
Category: