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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E18">Th20</font></span>: <a NAME="T20"><span class="comment"><font color="firebrick">:: MOD_2:20</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">UN</font> being   <a href="classes2.html#NM1" title="CLASSES2:NM.1">Universe</a><br/>  for <font color="Olive" title="b2">u</font> being    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of <font color="Olive" title="b1">UN</font> holds   <a href="ordinal1.html#K1" title="ORDINAL1:func.1">succ</a> <font color="Olive" title="b2">u</font> is    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of <font color="Olive" title="b1">UN</font></div></div>
