A. Helgesson

Propagation in Dielectric Slab Loaded Rectangular Waveguide

W. P. Ayres, P. Vartanian, A. Helgesson, 1958 .

Parametric frequency converters with nonlinear capacitance and resistance

W. Ku, A. Helgesson, P. Ross, 1963 .

Short-term stability of passive atomic frequency standards

R. F. Lacey, J. H. Holloway, A. Helgesson, 1965 .