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:L I S S , I N C .
chains united by disulfide bonds (Jones and Jomary, 2002; Leskov et al., 2003), which represents the mature, secreted form (sCLU, 75 kDa) of the protein.
Category: