On Mon, 7 Feb 2011, Paul Menzel wrote:

> thank you for your answer. `\overline` works as you say, but it looks
> typographically different in the respect that the bar is closer to the
> letter, which of course solves the issue for the inline fraction. For α
> this looks quite strange in my eyes. But I do not know a lot about
> typography.

IIRC, \overline is meant for long entities, like \overline{(a+b)}. For 
single letters, it is better to use the accent \bar.

Aditya