1. An essey on the properties of triangles inscribed and circumscribed about two given circles;Chapple W.;Misc. Curiosa,1746
2. Solutio facilis problematum quorundam geometricorum difficillimorum;Euler L.;Novi Commentarii academiae scientiarum Petropolitanae,1767
3. The new proof of Euler’s inequality using Spieker center;Krishna D. N. V.;Int. J. Math. Appl.,2015
4. A New Proof of Euler's Inequality
5. A new proof of Euler’s inradius - circumradius inequality;Pohoaţă C.;Gazeta Matematică Seria B,2010