Standard: http://www.w3.org/TR/xslt#element-value-of
value-of
Attributes: select, disable-output-escaping
Standard excerpt:
The xsl:value-of element is instantiated to create a text node in the result tree. The required select attribute is an expression;
this expression is evaluated and the resulting object is converted to a string as if by a call to the string function. The
string specifies the string-value of the created text node. If the string is empty, no text node will be created. The created
text node will be merged with any adjacent text nodes.
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