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<b>take </b>
 <a href="topreal1.html#K2">R^2-unit_square</a> 
;<br/>

<b>thus </b><a NAME="E1:12_1_1"/>
(  <a href="topreal1.html#K2">R^2-unit_square</a>  is <a href="topreal2.html#V1" target="_self">being_simple_closed_curve</a> &amp; not  <a href="topreal1.html#K2">R^2-unit_square</a>  is <a href="xboole_0.html#V1">empty</a> )
 ;<br/>


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