I need help integrating this unique function; its not taught in the text

Hey,

Im having trouble integrating this function: 1/1+Exp(-x^2)

None of the conventional methods I have learned will work on it. Substitution does not work, by parts does not work etc. And worst of all, I have yet to see any text give an example of how to inegrate it. All test only stick to giving examples where Exp is raised to a linear form of x, no nonlinear forms of x.

I have seen many examples were Exp is raised to a linear form of x, such as 1/1+Exp(-x) or 1/1+Exp(2x). Of course I have no trouble integrating these. But the same method I used to integrate these functions does not work on the function above. Could someone please tell me what the anti-derivative is for the function above, and the method that would be used to get it. Please post it step by step.

Thanx in advance