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 three parameters were based on the gesture coding system created by Church and Goldin-Meadow (1986): (a) shape of a hand gesture, (b) motion of a hand gesture, and (c) placement of a hand gesture.
Category: