1. A method for calculating the risk of type 2 error using non-parametric statistical tests;Arnfred;Ugeskr. L˦ger.,1983
2. Non-parametric confidence-intervals;Keiding;Ugeskr. L˦ger.,1984
3. Randomized trials in orthopaedics: Why, how, and when?;Laupacis;J. Bone Joint Surg.,1989
4. Nonparametrics. Statistical Methods Based on Ranks;Lehmann,1975