Attribute: background
In <mml:mo>
background CDATA #IMPLIED
In <mml:ms>
background CDATA #IMPLIED
In <mml:mspace>
background CDATA #IMPLIED
In <mml:mi>
background CDATA #IMPLIED
In <mml:mglyph>
background CDATA #IMPLIED
In <mml:mstyle>
background CDATA #IMPLIED
In <mml:mtext>
background CDATA #IMPLIED
In <mml:mn>
background CDATA #IMPLIED