@article{11125,
  author = {V. Čermák},
  title = {I. Individual Efficiency Curves for the Excitation of 23S and 21S States of Helium by Electron Impact  II. Retarding Potential Measurement of the Kinetic Energy of Electrons Released in Penning Ionization},
  year = {1966},
  number = {63},
  pages = {1-52},
  month = {1966-01},
  address = {Boulder},
  issn = {63},
}