Citation again

[Rub�n Barreto]

Hello,
I'm using the style dinat depending on natbib which gives me the citations as 
following:
(Gellner,1988) or if I want the page included (Gellner,1988,S.59).
How can I get the e.g. or vgl. inside the brackets?

Thank you.

Rub�n Barreto