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Flexible Implementations of Group Sequential Stopping Rules Using Constrained Boundaries
Burington, Bart E., (2003)
Exercises and Solutions in Biostatistical Theory by KUPPER, L. L., NEELON, B. H., and O’BRIEN, S. M.
Emerson, Scott S., (2011)
A Note on P-Values under Group Sequential Testing and Nonproportional Hazards
Gillen, Daniel L., (2005)