Document types handled so far are books, journal articles (with and without authors), book chapters, and presentations. This covers everything in the first two documents. Checking the previous entry to see if the name list is the same, and replacing with a dash, actually turns out to be unnecessary; the APA style guide doesn't seem to mention it, and shows examples of multiple items by the same authors with names shown in full (p.220, section 4.04).

Abstracted the regexp period-adding code into an external function:

<xsl:function name="mdh:addPeriodIfNeeded" as="xs:string">
    <!-- Incoming parameters -->
        <xsl:param name="inNode" as="node()" />
        <xsl:sequence 
            select="if (not(matches($inNode//text()[last()], '.*[\.\?!]{1}$')))
                then '.'
                else ''" />
    </xsl:function>