diff --git a/lectures/figures/traceability_via_commit.dia b/lectures/figures/traceability_via_commit.dia
deleted file mode 100644
index 62b472f..0000000
--- a/lectures/figures/traceability_via_commit.dia
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-        <dia:real val="0.40000000000000002"/>
-      </dia:attribute>
-      <dia:attribute name="text">
-        <dia:composite type="text">
-          <dia:attribute name="string">
-            <dia:string>#footer#</dia:string>
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-          <dia:attribute name="font">
-            <dia:font family="sans" style="80" name="Helvetica-Bold"/>
-          </dia:attribute>
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-        <dia:enum val="1"/>
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-        <dia:real val="0.5"/>
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-      <dia:attribute name="end_arrow_width">
-        <dia:real val="0.5"/>
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-        <dia:point val="37,13"/>
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-      <dia:attribute name="line_color">
-        <dia:color val="#444444"/>
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-        <dia:enum val="1"/>
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-    <dia:object type="Flowchart - Box" version="0" id="O17">
-      <dia:attribute name="obj_pos">
-        <dia:point val="53,8"/>
-      </dia:attribute>
-      <dia:attribute name="obj_bb">
-        <dia:rectangle val="52.95,7.95;59.05,10.05"/>
-      </dia:attribute>
-      <dia:attribute name="elem_corner">
-        <dia:point val="53,8"/>
-      </dia:attribute>
-      <dia:attribute name="elem_width">
-        <dia:real val="6"/>
-      </dia:attribute>
-      <dia:attribute name="elem_height">
-        <dia:real val="2"/>
-      </dia:attribute>
-      <dia:attribute name="border_width">
-        <dia:real val="0.10000000149011612"/>
-      </dia:attribute>
-      <dia:attribute name="border_color">
-        <dia:color val="#800080"/>
-      </dia:attribute>
-      <dia:attribute name="inner_color">
-        <dia:color val="#e19bff"/>
-      </dia:attribute>
-      <dia:attribute name="show_background">
-        <dia:boolean val="true"/>
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-      <dia:attribute name="padding">
-        <dia:real val="0.40000000000000002"/>
-      </dia:attribute>
-      <dia:attribute name="text">
-        <dia:composite type="text">
-          <dia:attribute name="string">
-            <dia:string>#issue#</dia:string>
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-          <dia:attribute name="font">
-            <dia:font family="sans" style="80" name="Helvetica-Bold"/>
-          </dia:attribute>
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-            <dia:real val="0.84666663408279419"/>
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-            <dia:point val="56,9.20538"/>
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-          <dia:attribute name="color">
-            <dia:color val="#000000"/>
-          </dia:attribute>
-          <dia:attribute name="alignment">
-            <dia:enum val="1"/>
-          </dia:attribute>
-        </dia:composite>
-      </dia:attribute>
-    </dia:object>
-    <dia:object type="Standard - PolyLine" version="0" id="O18">
-      <dia:attribute name="obj_pos">
-        <dia:point val="46,9"/>
-      </dia:attribute>
-      <dia:attribute name="obj_bb">
-        <dia:rectangle val="48.9999,8.6691;56.1118,9.3309"/>
-      </dia:attribute>
-      <dia:attribute name="poly_points">
-        <dia:point val="46,9"/>
-        <dia:point val="56,9"/>
-      </dia:attribute>
-      <dia:attribute name="line_color">
-        <dia:color val="#444444"/>
-      </dia:attribute>
-      <dia:attribute name="line_style">
-        <dia:enum val="4"/>
-      </dia:attribute>
-      <dia:attribute name="end_arrow">
-        <dia:enum val="1"/>
-      </dia:attribute>
-      <dia:attribute name="end_arrow_length">
-        <dia:real val="0.5"/>
-      </dia:attribute>
-      <dia:attribute name="end_arrow_width">
-        <dia:real val="0.5"/>
-      </dia:attribute>
-      <dia:connections>
-        <dia:connection handle="0" to="O11" connection="16"/>
-        <dia:connection handle="1" to="O17" connection="16"/>
-      </dia:connections>
-    </dia:object>
-    <dia:object type="Flowchart - Box" version="0" id="O19">
-      <dia:attribute name="obj_pos">
-        <dia:point val="47,4"/>
-      </dia:attribute>
-      <dia:attribute name="obj_bb">
-        <dia:rectangle val="46.95,3.95;55.05,7.05"/>
-      </dia:attribute>
-      <dia:attribute name="elem_corner">
-        <dia:point val="47,4"/>
-      </dia:attribute>
-      <dia:attribute name="elem_width">
-        <dia:real val="8"/>
-      </dia:attribute>
-      <dia:attribute name="elem_height">
-        <dia:real val="3"/>
-      </dia:attribute>
-      <dia:attribute name="border_width">
-        <dia:real val="0.10000000149011612"/>
-      </dia:attribute>
-      <dia:attribute name="border_color">
-        <dia:color val="#aa0000"/>
-      </dia:attribute>
-      <dia:attribute name="inner_color">
-        <dia:color val="#fb9a99"/>
-      </dia:attribute>
-      <dia:attribute name="show_background">
-        <dia:boolean val="true"/>
-      </dia:attribute>
-      <dia:attribute name="corner_radius">
-        <dia:real val="0.20000000000000001"/>
-      </dia:attribute>
-      <dia:attribute name="padding">
-        <dia:real val="0.20000000000000001"/>
-      </dia:attribute>
-      <dia:attribute name="text">
-        <dia:composite type="text">
-          <dia:attribute name="string">
-            <dia:string>#if issue ID
-provided (e.g. #42)#</dia:string>
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-          <dia:attribute name="font">
-            <dia:font family="sans" style="88" name="Helvetica-BoldOblique"/>
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-            <dia:real val="0.84666663408279419"/>
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-          <dia:attribute name="pos">
-            <dia:point val="51,5.28205"/>
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-          <dia:attribute name="color">
-            <dia:color val="#000000"/>
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-          <dia:attribute name="alignment">
-            <dia:enum val="1"/>
-          </dia:attribute>
-        </dia:composite>
-      </dia:attribute>
-    </dia:object>
-  </dia:layer>
-</dia:diagram>
diff --git a/lectures/figures/traceability_via_commit.png b/lectures/figures/traceability_via_commit.png
deleted file mode 100644
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