Compton Wavelength, h and h bar

[Badger01]

I have found 2 different representations of Compton wavelength:

$$\lambda$$=
$$\frac{h}{mc}$$
and
$$\frac{\bar{h}}{mc}$$
which of these is correct, and if both are right, how do you know when to use one or the other?
(note: the second equation contains a h bar as in " h bar = h/2pi ")

 

[ideasrule]

The proper Compton wavelength is the first equation. The second equation is the reduced Compton wavelength, and it's used more frequently because factors of 2pi pop up all over the place.