\[
\boxed{
 \left\{ at{\frac {\rm d}{{\rm d}t}}x \left( t \right) =bc \left( y \left( t \right) -z \left( t \right)  \right) ,bt{\frac {\rm d}{{\rm d}t}}y \left( t \right) =ca \left( z \left( t \right) -x \left( t \right)  \right) ,ct{\frac {\rm d}{{\rm d}t}}z \left( t \right) =ab \left( x \left( t \right) -y \left( t \right)  \right)  \right\} }
\]