@misc{indiciae98020c71f7db,
  title = {Null functions and eigenfunctions: tools for the analysis of imaging systems.},
  author = {H H Barrett and J N Aarsvold and T J Roney},
  year = {1991},
  url = {https://pubmed.ncbi.nlm.nih.gov/1988975/},
  note = {Source identifier: 1988975}
}