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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E22">Th21</font></span>: <a NAME="T21"><span class="comment"><font color="firebrick">:: TOPALG_6:21</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">T</font> being    <a href="pre_topc.html#L1" title="PRE_TOPC:struct.1">TopStruct</a>  holds   <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a>  is   <a href="topalg_6.html#NM1" title="TOPALG_6:NM.1">Curve</a> of <font color="Olive" title="b1">T</font></div></div>
