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:…around the soccer field (outside the touch and goal lines, which were extensions of the halfway line or penalty area approximately 3–30 m from each line) because multiple perpendicular views were recommended to obtain more accurate results using the MBIM technique (Krosshaug and Bahr, 2005).
Category: