Author: Mehta, C.R. N.R.P.Tsiatis, A.Biometrics, 50(4), p. 1042. Mehta, C.R., Patel, N.R., Senchaudhuri, P. and Tsiatis, A. http://www.cytel.com/hubfs/0-library-0/pdfs/Exact-Inference---MEHTA-PATEL-SENCHAUDHURI-TSIATIS-Exact-Permutational-Tests-for-Group-Sequential-Clinical-Trials-BIOMETRICS-1994.pdf?t=1484145078191 Interest: Compass