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:This is achieved by initializing the preference vector with the expression levels of the genes in the bicluster at each particular time point and diffuse them using a random walk based on the heat kernel rank, recently shown to perform better in comparison to PageRank [32].
Category: