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:Examples include minimum variance portfolio (Jorion, 1985; 1986), short-sell constrained minimum variance portfolios (Jagannathan and Ma, 2003), the equally weighted diversification (DeMiguel, Garlappi and Uppal, 2009), and other modifications to the mean-variance portfolio rule (see, e.g., Pesaran…
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