Theoretical derivation
Rodney Brookes and Giovanni di-Chiro (1976)
Statistical limitations in x-ray reconstructive tomography
Medical Physics Vol 3, No 4 July 1976
Riederer S.J., Pelc N.J. and Chesler D.A. (1978)
The Noise Power Spectrum in Computed Tomography
Physics in Medicine and Biology 1978 23(3), 446-454