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<div><span class="kw">theorem </span><a NAME="T18"><span class="comment"><font color="firebrick">:: BCIALG_4:18</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   <a href="binop_1.html#K3" title="BINOP_1:func.3">the_unity_wrt</a>  the <a href="bcialg_4.html#U1" title="BCIALG_4:sel.1">ExternalDiff</a> of <font color="Olive" title="b1">X</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="struct_0.html#K4" title="STRUCT_0:func.4">0.</a> <font color="Olive" title="b1">X</font></div></div>
