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:Single-category classification: We learned four types of interpretable CNNs based on the AlexNet, VGG-M, VGGS, and VGG-16 structures to classify each category in the ILSVRC 2013 DET Animal-Part dataset [36], the CUB2002011 dataset [30], and the Pascal VOC Part dataset [3].
Category: