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:After having estimated the TVAR for a given lag of the threshold variable, we perform a sup-LR test (Hansen, 1999; Lo and Zivot, 2001; Galvão, 2003; Clements and Galvão, 2004), in order to check the robustness of the results provided by the Tsay tests as to possible small-sample biases.
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