A possible integral representation of double commutators allowing non-vanishing mass of intermediate states is obtained. As expected, it reduces to Dyson's result on putting the masses to be zero. A discussion is also given showing how dispersive relatsions for non-forward scattering can be obtained on assuming the fourier transform F(q0, q) of the usual N|[j(x/2),j(-x/2)]|pN> to vanish not only for certain real q but also for asmall interval of imaginary q. It is pointed out that similar assumption is actually involved in customary proofs of dispersive relations.

Curves giving the cutoff frequencies of some modes and the power carrying capacity of the lowest propagating mode and an equation giving the attenuation constant are presented for a ridge coaxial waveguide. It is shown that the ridge coaxial waveguide has very low cutoff frequencies and rather great higher-mode seperation which also are properties of the coaxial TEM mode.

Cascade curves for high energy positrons are measured by Y. Plokoskin and the writer. Empirical formulas approximating the cascade curves were determined. Some new methods determining the energy of high energy electrons (or γ quantas) were suggested.