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:…of the precentral sulcus, superior to the cingulate sulcus (or the paracingulate sulcus, when present), and behind the coronal plane perpendicular to the anterior commissure – posterior commissure (AC – PC) line and tangent to the posterior margin of the AC (Chainay et al. 2004; Fink et al. 1997).
Category: