J. L. Johnson, K. E. Muller, J. C. Slaughter, M. . J. . Gurka, M. . J. . Gribbin, and S. L. Simpson, “POWERLIB: SAS/IML Software for Computing Power in Multivariate Linear Models”, J. Stat. Soft., vol. 30, no. 5, pp. 1–27, Apr. 2009.