Frank Morring Jr.: ULA, XCOR to Develop Upper-Stage Engine. In: Aviation Week. 23. März 2011, abgerufen am 17. April 2013 (englisch): „United Launch Alliance (ULA) and XCOR Aerospace are planning a joint effort to develop a low-cost upper-stage engine in the same class as the venerable RL-10, using technology XCOR is developing for its planned Lynx suborbital spaceplane. The two companies have been testing actively cooled aluminum nozzles XCOR is developing for its liquid oxygen/kerosene 5K18 engine for the Lynx, a reusable two-seat piloted vehicle the company plans to use for commercial research and tourist flights.“
mrt.com
Kathleen Petty: A look at XCOR. Midland Reporter Telegram, 7. Juli 2012, abgerufen am 24. November 2015 (englisch).
Products Overview. XCOR Aerospace, archiviert vom Original (nicht mehr online verfügbar) am 25. November 2010; abgerufen am 17. April 2013 (englisch): „Twin 400 lb-thrust XR-4A3 engines aboard the EZ-Rocket" (with in-flight photograph) ... "Another engine that we have developed in parallel is the XR-4K14, ... a 1,500 lb thrust regeneratively cooled LOX and pump-fed kerosene system ... used as the Rocket Racer aircraft's main engine.“
Allison Gatlin: XCOR performance tested. Antelope Valley Press, 11. Juli 2008, archiviert vom Original (nicht mehr online verfügbar) am 15. Juli 2009; abgerufen am 17. April 2013.
Products Overview. XCOR Aerospace, archiviert vom Original (nicht mehr online verfügbar) am 25. November 2010; abgerufen am 17. April 2013 (englisch): „Twin 400 lb-thrust XR-4A3 engines aboard the EZ-Rocket" (with in-flight photograph) ... "Another engine that we have developed in parallel is the XR-4K14, ... a 1,500 lb thrust regeneratively cooled LOX and pump-fed kerosene system ... used as the Rocket Racer aircraft's main engine.“
Allison Gatlin: XCOR performance tested. Antelope Valley Press, 11. Juli 2008, archiviert vom Original (nicht mehr online verfügbar) am 15. Juli 2009; abgerufen am 17. April 2013.
Countdown has begun for SXC (Memento vom 27. Dezember 2014 im Internet Archive) „Early next year, we will make the first sub-orbital flight, after which the final development will speed up tremendously. According to our schedule, we will be ready for commercial take-off by the end of 2013“