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<b>set </b><font color="Maroon">c<sub>2</sub></font> =  <a href="xboole_0.html#K1">{}</a> ;<br/>
<a NAME="E1:15_1_1"/>
 <a href="xboole_0.html#K1">{}</a>  <a href="tarski.html#R1">c=</a>  <a href="zfmisc_1.html#K1">bool</a> <font color="Maroon">c<sub>1</sub></font>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T2">XBOOLE_1:2</a></i>;<br/>
<b>then reconsider </b><font color="Maroon">c<sub>3</sub></font> =  <a href="xboole_0.html#K1">{}</a>  as   <a href="setfam_1.html#NM1">Subset-Family</a> of <font color="Maroon">c<sub>1</sub></font> ;<br/>
<b>take </b>
<font color="Maroon">c<sub>3</sub></font>
;<br/>

<b>thus </b><a NAME="E3:15_1_1"/>
<font color="Maroon">c<sub>3</sub></font> is <a href="taxonom2.html#V3" target="_self">hierarchic</a>
 <b>by </b><i><a class="ref" href="taxonom2.html#T6" target="_self">Th6</a></i>;<br/>


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