Use formula for the integration of the product of 3 MeijerG function?

Questions
1

I am trying to use the formula for the integration of the product of 3 MeijerG functions in the following link:

However, the following remark is mentioned in ( Meijer G-function: Integration ) :

Remark: This relationship only holds true when the parameters satisfy certain
well-specified restrictions.

what is the reference for this sentence to be able to use the conversion in the formula?
Thank you in advance

2

Did you check the subsection below that, under “Notations for conditions of convergence of generalization of classical Meijer’s integral from two G functions”?

3

the title said for 2 G functions, are they applicable for the 3 G case