57. U. S. Patent #3,572,928, John Decker, Jr. and Martin O. Harwit, Patented March 30, 1971, "Aircraft Proximity Warning System.", March 30, 1971,

57. U. S. Patent #3,572,928, John Decker, Jr. and Martin O. Harwit, Patented March 30, 1971, "Aircraft Proximity Warning System.", March 30, 1971,, Box: 21, Folder: 31. Martin Harwit papers, 14-7-2402. Division of Rare and Manuscript Collections. https://archives.library.cornell.edu/repositories/2/archival_objects/174408 Accessed January 23, 2026.