Process validation for one product with diff strength

I’m working in pharmaceutical co. in validation dept. & i need any one to help me as we are performing process validation for a product with different strength,i know that we can perform validation over 3 batches of the lowest strength & one of each of the remaining ones,but another criteria was suggested to perform validation over 2 batches only of each strength including the smallest one,can any one help me please & tell me which criteria to follow & provide me with a reference to that criteria& thank you all