Chang, M. N. (1989), "Confidence Intervals for a Normal Mean Following a Group Sequential Test," Biometrics, 45, 247–254.

Chang, M. N., Gould, A. L., and Snapinn, S. M. (1995), "P-values for Group Sequential Testing," Biometrika, 82, 650–654.

Chow, S. C. and Liu, J. P. (1998), Design and Analysis of Clinical Trials, Concept and Methodologies, New York: John Wiley & Sons.

Chow, S. C., Shao, J., and Wang, H. (2003), Sample Size Calculations in Clinical Research, Boca Raton, FL: CRC Press.

Cox, E. R. (1972), "Regression Models and Life-Tables (with Discussion)," Journal of the Royal Statistical Society, B, 34, 187–220.

Cui, L., Hung, H. M. J., and Wang, S. (1999), "Modification of Sample Size in Group Sequential Clinical Trials," Biometrics, 55, 853–857.

DeMets, D. L., Furberg, C. D., and Friedman, L. M. (2006), Data Monitoring in Clinical Trials, New York: Springer.

Dmitrienko, A., Molenberghs, G., Chuang-Stein, C., and Offen, W. (2005), Analysis of Clinical Trials Using SAS: A Practical Guide, Cary, NC: SAS Institute Inc.

Ellenberg, S. S., Fleming, T. R., and DeMets, D. L. (2003), Data Monitoring Committees in Clinical Trials, New York: John Wiley & Sons.

Emerson, S. S. (1996), "Statistical Packages for Group Sequential Methods," The American Statistician, 50, 183–192.

Emerson, S. S. and Fleming, T. R. (1989), "Symmetric Group Sequential Designs," Biometrics, 45, 905–923.

Emerson, S. S. and Fleming, T. R. (1990), "Parameter Estimation Following Group Sequential Hypothesis Testing," Biometrika, 77, 875–892.

Emerson, S. S., Kittelson, J. M., and Gillen, D. L. (2005), "On the Use of Stochastic Curtailment in Group Sequential Clinical Trials," UW Biostatistics Working Paper Series,

Fairbanks, K. and Madsen, R. (1982), "P Values for Tests Using a Repeated Significance Test Design," Biometrika, 69, 69–74.

Food and Drug Administration (1998), "E9: Statistical Principles for Clinical Trials," Federal Register, 63 (179), 49583–49598.

Herson, J. (1979), "Predictive Probability Early Termination for Phase II Clinical Trials," Biometrics, 35, 775–783.

Hwang, I. K., Shih, W. J., and DeCani, J. S. (1990), "Group Sequential Designs Using a Family of Type I Error Probability Spending Functions," Statistics in Medicine, 9, 1439–1445.

Jennison, C. and Turnbull, B. W. (2000), Group Sequential Methods with Applications to Clinical Trials, New York: Chapman & Hall.

Kim, K. and Tsiatis, A. A. (1990), "Study Duration for Clinical Trials with Survival Response and Early Stopping Rule," Biometrics, 46, 81–92.

Kittelson, J. M. and Emerson, S. S. (1999), "A Unifying Family of Group Sequential Test Designs," Biometrics, 55, 874–882.

Lan, K. K. G. and DeMets, D. L. (1983), "Discrete Sequential Boundaries for Clinical Trials," Biometrika, 70, 659–663.

Lan, K. K. G., Lachin, J. M., and Bautista, O. (2003), "Over-ruling a Group Sequential Boundary: A Stopping Rule versus a Guideline," Statistics in Medicine, 22, 3347–3355.

Lan, K. K. G., Simon, R., and Halperin, M. (1982), "Stochastically Curtailed Tests in Long-Term Clinical Trials," Sequential Analysis, 1, 207–219.

McCullagh, P. and Nelder, J. A. (1989), Generalized Linear Models, Second Edition, New York: Chapman & Hall/CRC.

Mehta, C. R. and Tsiatis, A. A. (2001), "Flexible Sample Size Considerations under Information Based Interim Monitoring," Drug Information Journal, 35, 1095–1112.

O’Brien, P. C. and Fleming, T. R. (1979), "A Multiple Testing Procedure for Clinical Trials," Biometrics, 35, 549–556.

Proschan, M. A., Lan, K. K. G., and Wittes, J. T. (2006), Statistical Monitoring of Clinical Trials, New York: Springer.

Rosner, G. L. and Tsiatis, A. A. (1988), "Exact Confidence Intervals Following a Group Sequential Trial: A Comparison of Methods," Biometrika, 75, 723–729.

Rudser, K.D. and Emerson, S.S. (2007), "Implementing Type I & Type II Error Spending for Two-Sided Group Sequential Designs," Contemporary Clinical Trials, doi:10.1016/j.cct.2007.09.002.

Scharfstein, D. O. and Tsiatis, A. A. (1998), "The Use of Simulation and Bootstrap in Information-Based Group Sequential Studies," Statistics in Medicine, 17, 75–87.

Tsiatis, A. A. and Mehta C. R. (2003), "On the Inefficiency of the Adaptive Design for Monitoring Clinical Trials," Biometrika, 90, 367–378.

Tsiatis, A. A., Rosner G. L., and Mehta C. R. (1984), "Exact Confidence Intervals Following a Group Sequential Test," Biometrics, 40, 797–803.

Ware, J. H., Muller, J. E., and Braunwald, E. (1985), "The Futility Index: An Approach to the Cost-Effective Termination of Randomized Clinical Trials" American Journal of Medicine, 78, 635–643.

Whitehead, J. (1997), The Design and Analysis of Sequential Clinical Trials, Revised Second Edition, Chichester: John Wiley & Sons.