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:cresylglucuronide (pCG), p-cresylsulfate (pCS), indole-3acetic acid (IAA), and 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (CMPF) [9–19], all solutes of pathophysiological relevance.
Category: