The difficulty, as in all this work, is to find a notation which is both concise and intelligible to at least two people of whom one may be the author.
with Abdus Salam. (October 1951). "The Renormalization of Meson Theories". Reviews of Modern Physics23 (4): 311-314. About the difficulty to express renormalization in quantum field theories. Also known as the Salam criterion.