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<div><span class="kw">theorem </span><a NAME="T27"><span class="comment"><font color="firebrick">:: CARD_1:27</font></span><br/></a><div class="add"> <a href="card_1.html#K1" title="CARD_1:func.1">card</a> <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="ordinal1.html#K5" title="ORDINAL1:func.5">0</a>  ;<br/></div></div>
