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:Laboratory parameters considered in this study were those already found significantly different between early PMF and WHO-ET: Hb (g/dL), WBC (3109/L), PLT (3109/L), and LDH (mU/mL).
Category: