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:While serum glucose was estimated by the modified glucose oxidase method, using GOD-POD kits (Glaxo India Ltd, Mumbai, India); for the hepatic LPO, SOD, CAT and GSH routine
protocols, followed earlier in our laboratory, were used (Jatwa and Kar, 2006; Panda and Kar, 2006).
Category: