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:The atlases used were created by standardized anatomic labeling of multiple subjects linearly registered to MNI-152 standard space [13,14], and the same type of registration method and tool was used in our study to reduce systematic errors introduced by differing registration methods.
Category: