@misc{indiciae0c20c657c504,
  title = {Electronically tuned optical filters},
  author = {Castellano, J. P. and Heilmeier, G. H. and Mc Caffrey, M. T. and Pasierb, E. F., Jr.},
  year = {1969},
  url = {https://ntrs.nasa.gov/citations/19690023974},
  note = {Source identifier: 19690023974}
}