[texhax] natbib: same authors and year citations

[jtzzaa11-texhax at yahoo.com]

Hi,

I'm using natbib for referencing, and have several citations by the same author within the same year, for example:
Smith, A. (2001) paper 1
Smith, A. (2001) paper 2

When I cite these in the text, the citations are identical, for example, Jones A. (2010) for both paper 1 and paper 2. 

Doesn't natbib assign different citation labels to different entries automatically? for example. generating Jones (2010)a, Jones (2010)b .

If it doesn't, is there a way to automatically create different citation labels for such references (same authors and same year)?.

TIA,
Joel.