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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E12">Th19</font></span>: <a NAME="T19"><span class="comment"><font color="firebrick">:: TREES_2:19</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">W</font> being   <a href="trees_1.html#NM1" title="TREES_1:NM.1">Tree</a> holds   <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a>  is    <a href="trees_2.html#M1" title="TREES_2:mode.1">Chain</a> of <font color="Olive" title="b1">W</font></div></div>
