Key points are not available for this paper at this time.
Unlike the book by Bjorken and Drell this work is labelled as 'Introductory' and in this case this term must be understood to imply treatment by methods more elementary than those reasonably employed in teaching intending specialists. This present volume has its origins in lecture courses delivered, evidently to not too highly specialized audiences, and the style is fairly leisurely, with a great deal of the argument spelled out in algebraic detail.
N. Kemmer (Mon,) studied this question.