@misc{indiciaeb0e4082d3279,
  title = {Ion propulsion cost effectivity},
  author = {Zafran, S. and Biess, J. J. and Callens, R. A.},
  year = {1979},
  url = {https://ntrs.nasa.gov/citations/19800029142},
  note = {Source identifier: 19800029142}
}