1. H. Yukawa:Proc. Phys. Math. Soc. Japan,17, 48 (1935).
2. Unitsh=c=1 are used throughout (the Compton wavelength of the pion is 1/m π=1.4296 fm; the conversion factor ishc=197.3286 MeV fm).
3. Notationx=m πr will be used throughout.
4. C. Møller andL. Rosenfeld:Kgl. Danske Vid. Sels. Math. Fys. Medd,17, 8 (1940).
5. T. A. Minelli, A. Pascolini andC. Villi:Atti dell’Istituto Veneto di Scienze, Lettere ed Arti, CXLVI, 29 (1987–88).