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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E17">Th17</font></span>: <a NAME="T18"><span class="comment"><font color="firebrick">:: CARDFIL4:18</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">X</font> being   non  <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>   <a href="hidden.html#M2" title="HIDDEN:mode.2">set</a> <br/>  for <font color="Olive" title="b2">cF</font> being    <a href="card_fil.html#M1" title="CARD_FIL:mode.1">Filter</a> of <font color="Olive" title="b1">X</font> holds  <font color="Olive" title="b2">cF</font> is   <a href="subset_1.html#V1" title="SUBSET_1:attr.1">proper</a>  <a href="waybel_0.html#NM4" title="WAYBEL_0:NM.4">Filter</a> of <span class="p1">(<span class="default"><a href="yellow_1.html#K2" title="YELLOW_1:func.2">BoolePoset</a> <font color="Olive" title="b1">X</font></span>)</span></div></div>
