Question on MoM and performing 4-D integration

I analyze patch microstrip antenna using MoM, in order to compute the impedance matrix, I need to perform 4-D integration,whose kernel is green function and the base function(test function).a paper proposed the methods to reduce the 4-D integration to 1-D integration,but the method only limit to the expand function(roof-top function) of patch surface current ,i wonder if the method can also be used in the integration whose kernel is the green function and expand function of coxial probe current and attachment model?

thanks a lot