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:…(2008), 135, 795–806. f 2008 Cambridge University Press doi:10.1017/S0031182008000292 Printed in the United Kingdom
Downloaded: 30 Jun 2008journals.cambridge.org
variability in parasites (Pieniazek et al. 1999; Chicharro, Jimenez and Alvar, 2003; Pratlong et al. 2003).
Category: