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:The oils, which are generally composed of complex mixtures of monoterpenes, phenols, and sesquiterpenes, have demonstrated insecticidal, repellent, antifeedant and insect growth regulatory properties, and suppression of adult insect fertility and oviposition [4,6].
Category: