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:…and glucose and then were tested, within 10 min of their collection , (a) with the modified Griess nitrite method (Cruickshank & Moyes, 1914; Smith et al., 1961; Smith & Schmidt, 1962), (b) with the glucose consumption detecting test (Scherst6n & Fritz, 1967; Schersten, Fritz & Kohler, 1967).
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