P. 195, line 1

The equation should be:

$\frac{d}{d t} [\begin{matrix} ξ_{1} \\ ξ_{2} \\ ξ_{3} \\ ξ_{4} \end{matrix}] = [\begin{matrix} ξ_{2} \\ \frac{1}{m_{1}} (- b_{1} ξ_{2} - k_{1} ξ_{1} + k_{2} ξ_{3} - k_{2} ξ_{1} + b_{2} ξ_{4} - b_{2} ξ_{2}) \\ ξ_{4} \\ \frac{1}{m_{2}} (- k_{2} ξ_{3} + k_{2} ξ_{1} - b_{2} ξ_{4} + b_{4} ξ_{2}) \end{matrix}]$