60. U. S. Patent #3,578,980, John Decker, Jr. and Martin O. Harwit, patented May 18, 1971, "Spectral Analysis Using Masks Having Different Combinations of Transmitting and Non-Transmitting Portions.", May 18, 1971,

60. U. S. Patent #3,578,980, John Decker, Jr. and Martin O. Harwit, patented May 18, 1971, "Spectral Analysis Using Masks Having Different Combinations of Transmitting and Non-Transmitting Portions.", May 18, 1971,, Box: 21. Martin Harwit papers, 14-7-2402. Division of Rare and Manuscript Collections. https://archives.library.cornell.edu/repositories/2/archival_objects/174411 Accessed January 22, 2026.