  New results on the oscillation of solutions of $f''+A(z)f=0$ and on the
growth of solutions of $f''+A(z)f'+B(z)f=0$ are obtained, where $A$ and $B$ are
entire functions. Petrenko's magnitudes of deviation of $g$ with respect to
$\infty$ play a key r\^ole in the results, where $g$ represents one of the
coefficients $A$ or $B$. These quantities are defined by $\beta^-(\infty,g) =
\liminf_{r\to\infty} \frac{\log M(r,g)}{T(r,g)}$ and $\beta^+(\infty,g) =
\limsup_{r\to\infty} \frac{\log M(r,g)}{T(r,g)}$.
