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<b>let </b><font color="Maroon">S1</font> be   <a href="catalg_1.html#NM1">Signature</a>;<br/><b>let </b><font color="Maroon">S2</font> be    <a href="algspec1.html#M2" target="_self">Extension</a> of <font color="Maroon">S1</font>;<br/><b>let </b><font color="Maroon">S3</font> be    <a href="algspec1.html#M2" target="_self">Extension</a> of <font color="Maroon">S2</font>;<br/>





<a NAME="E1:52"/>
( <font color="Maroon">S1</font> is    <a href="instalg1.html#M1">Subsignature</a> of <font color="Maroon">S2</font> &amp; <font color="Maroon">S2</font> is    <a href="instalg1.html#M1">Subsignature</a> of <font color="Maroon">S3</font> )
 
<b>by </b><i/>;<br/>
<a NAME="E2:52"/><b>then </b>
<font color="Maroon">S1</font> is    <a href="instalg1.html#M1">Subsignature</a> of <font color="Maroon">S3</font>
 
<b>by </b><i><a class="ref" href="instalg1.html#T17">INSTALG1:17</a></i>;<br/>
<b>hence </b><a NAME="E3:52"/>
<font color="Maroon">S3</font> is    <a href="algspec1.html#M2" target="_self">Extension</a> of <font color="Maroon">S1</font>
 <b>by </b><i/>;<br/>


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