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<b>let </b><font color="Maroon">c<sub>1</sub></font> be    <a href="orders_2.html#L1">RelStr</a> ;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font> be    <a href="hidden.html#M1">set</a> ;<br/>



<a NAME="E1:35"/>
( <font color="Maroon">c<sub>2</sub></font> is  <a href="waybel_0.html#V2">filtered</a> <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">c<sub>1</sub></font> iff <font color="Maroon">c<sub>2</sub></font> is  <a href="waybel_0.html#V2">filtered</a> <a href="struct_0.html#NM2">Subset</a> of <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="yellow_7.html#NK1" target="_self">opp</a> </span>)</span> <a href="lattice3.html#K7">~</a> </span>)</span> )
 
<b>by </b><i><a class="ref" href="waybel_0.html#T4">WAYBEL_0:4</a></i>;<br/>
<b>hence </b><a NAME="E2:35"/>
( <font color="Maroon">c<sub>2</sub></font> is  <a href="waybel_0.html#V1">directed</a> <a href="struct_0.html#NM2">Subset</a> of <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="yellow_7.html#NK1" target="_self">opp</a> </span>)</span> iff <font color="Maroon">c<sub>2</sub></font> is  <a href="waybel_0.html#V2">filtered</a> <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">c<sub>1</sub></font> )
 <b>by </b><i><a class="ref" href="yellow_7.html#T26" target="_self">Th26</a></i>;<br/>


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