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<b>consider </b><font color="Maroon">c<sub>1</sub></font> being   <a href="trees_1.html#NM1">Tree</a>;<br/>
<a NAME="E2:3_1_1"/>
<font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#R2">in</a>  <a href="trees_3.html#K1" target="_self">Trees</a> 
 
<b>by </b><i><a class="ref" href="trees_3.html#D1" target="_self">Def1</a></i>;<br/>
<b>hence </b><a NAME="E3:3_1_1"/>
not  <a href="trees_3.html#K1" target="_self">Trees</a>  is <a href="xboole_0.html#V1">empty</a>
 ;<br/>


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