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 presence and severity of atrial septal aneurysm were classified in accordance with Olivares et al.(13) Hypertrophic rims were defined as having a thickness ‚â•8mm, whereas lipomatosis was defined as thickness of ‚â•15mm, on intracardiac echocardiogram study.
Category: