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:Its levels can also be elevated during menstruation or pregnancy, as well as in other benign gynaecological conditions, such as endometriosis, peritonitis or cirrhosis, especially with ascites production (Tuxen et al, 1995, Meyer and Rustin, 2000).
Category: