Stead, Chris (2011). «The Best Game Engines of this Generation»(en inglés). IGN. Consultado el 13 de mayo de 2011. «Although the original game in the series ran off the id Tech 3 engine, for the highly regarded Call of Duty 2 the developer built its own in-house middleware which, until recently, had no official name. When questioned at E3 this year, however, we were told by an Infinity Ward rep that the upcoming Modern Warfare 2 would be running on the IW 4.0 engine, a generation beyond what we saw in the so-spectacular-it-hasn't-aged-a-bit Call of Duty 4, released in 2007».
