1. Importance of prognostic factors in the analysis of data from clinical trials;Armitage;Controlled Clin Trials,1981
2. Identification of prognostic factors;Byar,1988
3. Regression models and life-tables (with discussion);Cox;J R Stat Soc B,1972
4. Choosing covariates in the analysis of clinical trials;Beach;Controlled Clin Trials,1989
5. Sample-size formula for the proportional-hazards regression model;Schoenfeld;Biometrics,1983