only the estimated coefficient

Hi,

Which could be the reason that Stata shows me only the estimated coefficient?:


------------------------------------------------------------------------------
| Robust
ln_TRADE | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------

ln_DIST | -.7334557 . . . . .
CNTG | 1.421494 . . . . .
LANG | -3.674322 . . . . .
CLNY | 6.189377 . . . . .
_cons | 17.52462 . . . . .
--------------------------------------------------------------------------------------


Thanks!