2.2.8 [XML] Section 4.2.2, External Entities
An XML processor attempting to retrieve the entity's content may use any combination of the public and system identifiers as well as additional information outside the scope of this specification to try to generate an alternative URI reference. If the processor is unable to do so, it MUST use the URI reference specified in the system literal. Before a match is attempted, all strings of white space in the public identifier MUST be normalized to single space characters (#x20), and leading and trailing white space MUST be removed.
IE9 Mode, IE10 Mode, IE11 Mode, and EdgeHTML Mode (All Versions)
External entities are not resolved.
If one of the following public identifiers is used, the entities that are defined by XHTML are resolved:
//W3C//DTD XHTML 1.0 Transitional//EN
//W3C//DTD XHTML 1.1//EN
//W3C//DTD XHTML 1.0 Strict//EN
//W3C//DTD XHTML 1.0 Frameset//EN
//W3C//DTD XHTML Basic 1.0//EN
//W3C//DTD XHTML 1.1 plus MathML 2.0//EN
//W3C//DTD XHTML 1.1 plus MathML 2.0 plus SVG 1.1//EN
//W3C//DTD MathML 2.0//EN
//WAPFORUM//DTD XHTML Mobile 1.0//EN