Calculation of Cutoff Wavenumbers For TE and TM Modes in Tubular Lines with Offset Center Conductor (Additional Comments)

Although Vishen et al. refer to the early work of Veselov and Semenov, no comparison is made between their formulation and the one found in. I fail to recognize any essential differences between the two approaches. Furthermore, the authors state that the technique "based on Graf\´s addition theorem for Bessel functions" was developed by Singh and Kohtari, whereas in fact it appears that the same technique was employed in considerably earlier.