Change:

 <xsl:template 
match="contrib"><au><xsl:apply-templates/></au></xsl:template>

to

 <xsl:template 
match="contrib"><au>
<xsl:apply-templates select="./given-names"/>
<xsl:apply-templates select="./surname"/>
<xsl:apply-templates select="./qualifications"/>
</au></xsl:template>

Not tested so may have spell mistake but it is the way.

HTH,
Pankaj