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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E16">Th18</font></span>: <a NAME="T19"><span class="comment"><font color="firebrick">:: BCIALG_4:19</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">X</font> being   <a href="bcialg_4.html#NM1" title="BCIALG_4:NM.1">BCI-Algebra_with_Condition(S)</a> holds   the <a href="bcialg_4.html#U1" title="BCIALG_4:sel.1">ExternalDiff</a> of <font color="Olive" title="b1">X</font> is  <a href="setwiseo.html#V1" title="SETWISEO:attr.1">having_a_unity</a> </div></div>
