Citations:required

1. • 1934, A. C. Aitken, "Note on Selection from a Multivariate Normal Population", Proceedings of the Edinburgh Mathematical Society 4, page 106:

     From a population characterised by variables $x,y,z$,Template:... a sub-population is extracted by selection in $x$ aloneTemplate:.... It is required to determine the new values, in the selected population, of the means and variances of $y$ and $z$Template:....