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<div><span class="kw">theorem </span><a NAME="T4"><span class="comment"><font color="firebrick">:: BINTREE1:4</font></span><br/></a><div class="add"> <a href="trees_1.html#K2" title="TREES_1:func.2">elementary_tree</a> <a href="numbers.html#K5" title="NUMBERS:func.5">0</a> is  <a href="bintree1.html#V1" title="BINTREE1:attr.1">binary</a>  ;<br/></div></div>
