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 cartilage staining, embryos were fixed for 2 hours to overnight in buffered 4% formaldehyde, rinsed briefly in distilled water and transferred directly into a 0.1% solution of Alcian blue to stain overnight (Dingerkus and Uhler, 1977).
Category: