P. 210, line 1

The equation should be:

$\left[\begin{array}{c}{\xi }_1(t)\\ {\xi }_2(t)\end{array}\right]=e^t(\left[\begin{array}{c}1\\ 0\end{array}\right]\cos 2t-\left[\begin{array}{c}0\\ -1\end{array}\right]\sin 2t)-e^t(\left[\begin{array}{c}1\\ 0\end{array}\right]\sin 2t+\left[\begin{array}{c}0\\ -1\end{array}\right]\cos 2t)$

Return to errata.