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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E1">Lemma1</font></span>: <a NAME="T1"><span class="comment"><font color="firebrick">:: PREFER_1:1</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">A</font> being    <a href="hidden.html#M2" title="HIDDEN:mode.2">set</a>  holds   <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> ,<font color="Olive" title="b1">A</font>, <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a>  <a href="prefer_1.html#R1" title="PREFER_1:pred.1">are_mutually_disjoint</a> </div></div>
