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:…myocardial infarction, left ventricular dysfunction, myocardial stunning, paroxysmal AV blockade, as well as exercise induced
ventricular tachycardia and sudden cardiac death (Canyigit et al. 2009; Ferreira et al. 1991; Lazoura et al. 2010; Ozbag and Kervancioglu 2004; Santos et al. 2007).
Category: