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:…depth (Schneider, 2005a, 2008, 2010c), by minimizing the number of sums arising within the summand (Schneider, 2004, 2015), or minimizing the degree of the sums and products arising in the summands and multiplicands (Abramov, 1975; Paule, 1995; Schneider, 2005b, 2007a; Abramov and Petkovšek, 2010).
Category: