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:For this a pneumatic sensor (SIGaT¬Æ, Ganzoni, Switzerland) was used to receive the in vivo pressure dimensions at B- and C-Level based on a previous study (Gaied et al. 2006).
Category: