1. Ovrebo JP, Wood RC (1963) Apparatus for passive infrared range finding, US Patent 3,103,586
2. Jennes JR, Shimukonis FJ (1964) Apparatus for passive infrared range finding, US Patent 3,117,228
3. Jeffrey W et al (1994) Monocular passive ranging. In: Proceedings of IRIS targets, background and discrimination, vol II, pp 113–130
4. Evans HE et al (1995) The theory of single sensor altitude determination. In: Proceedings of the 1995 IEEE national aerospace and electronics conference, pp 782–786
5. Elser DA (1984) Time-to-go (TTG) determination in an IRST, Huges Aircraft Co. internal memorandum data