<box> (Box Function)
This element specifies the box function, which is used to group components of an equation. A boxed object can (for example) serve as an operator emulator with or without an alignment point, serve as a line break point, have associated <argSz>, or be grouped such as not to allow line breaks within.
The equation  uses a <box> around the double equal sign.
example: 
<m:r>
  <m:t>a</m:t>
</m:r>
<m:box>
  <m:boxPr>
    <m:opEmu	m:val="on"/>
    <m:aln/>
  </m:boxPr>
  <m:e>
      <m:r>
        <m:t>==</m:t>
      </m:r>
  </m:e>
</m:box>
<m:r>
  <m:t>b</m:t>
</m:r>
Parent Elements  | 
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The following XML Schema fragment defines the contents of this element:
<complexType name="CT_Box">
	<sequence>
	<element name="boxPr" type="CT_BoxPr" minOccurs="0"/>
	<element name="e" type="CT_OMathArg"/>
	</sequence>
</complexType>