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:This mode of translocation, known as ‘molecular ratchet’, can be imagined as ‘directed diffusion’ and is utilised by many other unrelated molecular machines of the modern cell, such as, for example, multi-subunit RNA polymerase (Abbondanzieri et al. 2005).
Category: