- https://sites.google.com/site/sovietaircrafttech/home
- https://archive.org/details/RP-21_Sapfir_radar_technical_manual/Aircraft%20radar%20station%20RP-21M%20page-1/
- http://www.flyshark.ayz.pl/Stacja_angielska/sapfir.htm
- https://svppbellum.blogspot.com/2018/12/il-mikoyan-gurevich-mig-21-in-cirillico.html