P. 206, lines 4 and 7

The right expression on line 4 should be:

${\hat {\xi }}^{1}=\left[{\begin{array}{c}{\hat {\xi }}_{1}^{1}\\{\hat {\xi }}_{2}^{1}\end{array}}\right]=\left[{\begin{array}{c}1\\-i\end{array}}\right].$

and the right expression on line 7 should be:

${\hat {\xi }}^{2}=\left[{\begin{array}{c}{\hat {\xi }}_{1}^{2}\\{\hat {\xi }}_{2}^{2}\end{array}}\right]=\left[{\begin{array}{c}1\\i\end{array}}\right].$

Return to errata.