At the moment I'm writing my doctors degree (clinical study,
dentistry). I'm using zotero with a modified citation style (former: Elsevir's Havard style). It nearly matches the style, which
is used in my university. The only problem:

When I cites two times from the same source there is a little « a » in
the citation. e.g.

(Roulet and Zimmer, 2003a).......................... (Roulet and
Zimmer, 2003b).

How can I change this. I can not find the
correct line. Here the code of my *.cls

<?xml version="1.0" encoding="UTF-8"?>
<?oxygen RNGSchema="http://xbiblio.svn.sourceforge.net/viewvc/*checkout*/xbiblio/csl/schema/trunk/csl.rnc" type="compact"?>
<style xmlns="http://purl.org/net/xbiblio/csl" class="in-text" xml:lang="en">
<info>
<title>UWH style (dev)</title>
<id>http://www.zotero.org/styles/elsevier-harvard</id>;
<link href="http://www.zotero.org/styles/elsevier-harvard"/>
<link href="http://www.elsevier.com/wps/find/journaldescription.cws_home/405853/authorinstructions#68000" rel="documentation"/>
<link href="http://www.zotero.org/styles/ecology-letters" rel="template"/>
<author>
<name>Philipp Hertenstein</name>
<email>philipp.hertenstein@gmx.de</email>
<category term="biology"/>
<category term="generic-base"/>
<category term="author-date"/>
<updated>2010-07-26T02:21:30+00:00</updated>
<rights>This work is licensed under a Creative Commons Attribution-Share Alike 3.0 License: http://creativecommons.org/licenses/by-sa/3.0/</rights>;
</info>
<macro name="container">
<choose>
<if type="chapter">
<text term="in" text-case="lowercase" prefix=", " suffix=": "/>
<names variable="editor translator" delimiter=", " suffix=", ">
<name name-as-sort-order="all" sort-separator=", "
initialize-with="." delimiter=", " delimiter-precedes-last="always"/>
<label form="short" text-case="capitalize-first" prefix=" (" suffix=".)"/>
</names>
<group delimiter=", ">
<text variable="container-title"/>
<text variable="collection-title"/>
</group>
</if>
<else-if type="book">
<group prefix=", " delimiter=", ">
<text variable="container-title"/>
<text variable="collection-title"/>
</group>
</else-if>
<else>
<group prefix=". " delimiter=", ">
<text variable="container-title" form="short"/>
<text variable="collection-title"/>
</group>
</else>
</choose>
</macro>
<macro name="author">
<names variable="author">
<name name-as-sort-order="all" sort-separator=", "
initialize-with="." delimiter=", " delimiter-precedes-last="always"/>
<label form="short" prefix=" (" suffix=".)" text-case="capitalize-first"/>
<substitute>
<names variable="editor"/>
<names variable="translator"/>
<text macro="title"/>
</substitute>
</names>
</macro>
<macro name="author-short">
<names variable="author">
<name form="short" and="text" delimiter=", " initialize-with=". "/>
<substitute>
<names variable="editor"/>
<names variable="translator"/>
<choose>
<if type="book">
<text variable="title" form="short" font-style="italic"/>
</if>
<else>
<text variable="title" form="short" quotes="true"/>
</else>
</choose>
</substitute>
</names>
</macro>
<macro name="access">
<choose>
<if type="webpage">
<group>
<text value="URL" suffix=" "/>
<text variable="URL"/>
</group>
</if>
</choose>
</macro>

<macro name="title">
<choose>
<if type="report thesis" match="any">
<text variable="title"/>
<group prefix=" (" suffix=")">
<text variable="genre"/>
<text variable="number" prefix=" No. "/>
</group>
</if>
<else-if type="book speech" match="any">
<text variable="title"/>
<text macro="edition" prefix=", "/>
</else-if>
<else-if type="webpage">
<text variable="title"/>
<text value="WWW Document" prefix=" [" suffix="]"/>
</else-if>
<else>
<text variable="title"/>
</else>
</choose>
</macro>
<macro name="publisher">
<choose>
<if type="report thesis" match="any">
<group delimiter=", ">
<text variable="publisher"/>
<text variable="publisher-place"/>
</group>
</if>
<else>
<group delimiter=", ">
<text variable="publisher"/>
<text variable="publisher-place"/>
</group>
</else>
</choose>
</macro>
<macro name="event">
<choose>
<if variable="event">
<text term="presented at" text-case="capitalize-first" suffix=" "/>
<text variable="event"/>
</if>
</choose>
</macro>
<macro name="issued">
<choose>
<if variable="issued">
<date variable="issued">
<date-part name="year"/>
</date>
</if>
<else-if variable="accessed">
<choose>
<if type="webpage">
<date variable="accessed">
<date-part name="year"/>
</date>
</if>
<else>
<text term="no date"/>
</else>
</choose>
</else-if>
<else>
<text term="no date"/>
</else>
</choose>
</macro>
<macro name="edition">
<group delimiter=" ">
<choose>
<if is-numeric="edition">
<number variable="edition" form="ordinal"/>
</if>
<else>
<text variable="edition" suffix="."/>
</else>
</choose>
<text value="ed"/>
</group>
</macro>
<macro name="locators">
<choose>
<if type="article-journal article-magazine article-newspaper" match="any">
<group prefix=" " delimiter=", ">
<group>
<text variable="volume"/>
</group>
<text variable="page"/>
</group>
</if>
<else-if type="book">
<group delimiter=", " prefix=". ">
<text macro="event"/>
<text macro="publisher"/>
</group>
</else-if>
<else-if type="chapter">
<group delimiter=", " prefix=". ">
<text macro="event"/>
<text macro="publisher"/>
<group>
<label variable="page" form="short" include-period="true" suffix=" "/>
<text variable="page"/>
</group>
</group>
</else-if>
</choose>
</macro>
<citation>
<option name="et-al-min" value="3"/>
<option name="et-al-use-first" value="1"/>
<option name="et-al-subsequent-min" value="2"/>
<option name="et-al-subsequent-use-first" value="1"/>
<option name="disambiguate-add-year-suffix" value="true"/>
<option name="disambiguate-add-names" value="true"/>
<option name="collapse" value="year"/>
<sort>
<key macro="issued"/>
<key macro="author"/>
</sort>
<layout prefix="(" suffix=")" delimiter="; ">
<group delimiter=", ">
<text macro="author-short"/>
<text macro="issued"/>
</group>
</layout>
</citation>
<bibliography>
<option name="hanging-indent" value="true"/>
<option name="entry-spacing" value="0"/>
<option name="line-spacing" value="1"/>
<sort>
<key macro="author"/>
<key macro="issued" sort="ascending"/>
</sort>
<layout>
<group suffix=".">
<text macro="author" suffix=","/>
<text macro="issued" prefix=" " suffix=". "/>
<group>
<text macro="title"/>
<text macro="container"/>
</group>
<text macro="locators"/>
</group>
<text macro="access" prefix=". "/>
</layout>
</bibliography>
</style>