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:In a number of cases this resulted in a similar effect on transcription, namely activation of cryptic splice sites and exon skipping (Gardella et al, 1996; Posteraro et al, 1998; Terracina et al, 1998; Weil et al, 1988).
Category: