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<div><span class="kw">theorem </span><a NAME="T40"><span class="comment"><font color="firebrick">:: TOPGEN_5:40</font></span><br/></a><div class="add"> <a href="topgen_5.html#K1" title="TOPGEN_5:func.1">y=0-line</a>  is   <a href="tops_1.html#V3" title="TOPS_1:attr.3">nowhere_dense</a>  <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <a href="topgen_5.html#K3" title="TOPGEN_5:func.3">Niemytzki-plane</a></div></div>
