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:Lim, Shanthikumar and Vahn, from their experiments [9], observed significant variation in the efficient mean-CVaR frontiers when the number of scenarios that is used to generate each frontier is small, even though the true mean is known in the TMEC problem or the mean is not taken into account in the GMC problem.
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