Using internal content and @select to set variable or param

An xsl:variable or xsl:param must not set its value both ways. When it carries a @select attribute and also has content, the binding is ambiguous, so keep only one.

Incorrect:

<xsl:variable name="physicist" select="'Isaac Newton'">
    Albert Einstein
</xsl:variable>

or:

<xsl:param name="physicist" select="'J.J. Thomson'">
    Max Planck
</xsl:param>

Correct:

<xsl:variable name="physicist">
    Marie Curie
</xsl:variable>

or:

<xsl:variable name="physicist" select="'Ernest Rutherford'"/>

or:

<xsl:param name="physicist">
    Galileo Galilei
</xsl:param>

or:

<xsl:param name="physicist" select="'Lev Landau'"/>