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:Under the notation in equation (13), the good-deal bounds are a coherent risk measure of Artzner et al. (1999), which searches for the infimum of all risk measures over an acceptance set. Delbaen (2002) further shows that any coherent risk measure can be expressed as a worst expected loss over a given set of probabilities and Jaschke and Küchler (2001) link the good-deal bounds to coherent risk measures by showing that the good-deal bounds are coherent valuation bounds.
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