Johnson, J. L., Muller, K. E., Slaughter, J. C., Gurka, M. . J. ., Gribbin, M. . J. . and Simpson, S. L. (2009) “POWERLIB: SAS/IML Software for Computing Power in Multivariate Linear Models”, Journal of Statistical Software, 30(5), pp. 1–27. doi: 10.18637/jss.v030.i05.