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## Main Question or Discussion Point

When we want to calculate the n-point function in the position space, it's always very difficult. For example, when we're calculate the 3-point function of [tex]\phi^3[/tex] theory in position space, we would get an integral

[tex]\int d^4 z \frac{1}{|z-x_1|^2|z-x_2|^2|z-x_3|^2}[/tex]

It seems hard to integrate it.

I'm wondering if anyone has already done this before. Or is there any theory to calculate these kind of integrals?

[tex]\int d^4 z \frac{1}{|z-x_1|^2|z-x_2|^2|z-x_3|^2}[/tex]

It seems hard to integrate it.

I'm wondering if anyone has already done this before. Or is there any theory to calculate these kind of integrals?