Dear Friends,

I need help with a result due to Levitan.

Please see the last paragraph of page 4 of the following paper:

http://www.emis.de/journals/EJDE/2007/163/rath.pdf
Above, $\displaystyle S$ is the set of continuous functions bounded below and above by $\displaystyle 3(1-p)/5$ (here $\displaystyle p$ is a positive constant less than $\displaystyle 1$) and $\displaystyle 1$, respectively, and that $\displaystyle B:S\to C([T_{0},\infty),\mathbb{R})$.

I really need help about finding a

__book__ reference for

*Levitan*'s result.

Many thanks!

**bkarpuz**