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:…excessive absorption of calcium from the intestine due to the increased vitamin D, excessive bone resorption, reduced renal excretion of calcium and increased total serum calcium due to increased protein bound and/or complexed calcium with normal ionized calcium levels (Rosol and Capen, 1997).
Category: