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:Whereas Lorden used crude upper bounds for the Type I error probability that are too conservative for practical applications, Bartroff and Lai (2008) overcome this difficulty by developing numerical methods to compute the Type I error probability and also extended the three-stage test to multiparameter and multi-armed settings, thus greatly broadening the scope of these efficient adaptive designs. A review of their method is given in Section 2.1. In Section 4 we prove the asymptotic optimality of these adaptive tests in the multiparameter case, extending Lorden’s (1983) result for the special case d = 1. Another new addition to this asymptotic optimality theory of adaptive designs is related to the problem of trial extension considered in Section 2.2. As pointed out by Cui et al. (1999), the issue of increasing the maximum sample size sometimes arises after interim analysis in group sequential trials.
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