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<b>let </b><font color="Maroon">c<sub>1</sub></font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font> be   <a href="zf_lang.html#NM2">ZF-formula</a>; <i><font color="Red">:: according to </font></i><a class="ref" href="zfrefle1.html#D1" target="_self">ZFREFLE1:def 1</a><br/>



<b>thus </b><a NAME="E1:5"/>
( <font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R2">in</a>  <a href="subset_1.html#K1">{}</a> <a href="zf_lang.html#K9">WFF</a>  implies <font color="Maroon">c<sub>1</sub></font> <a href="zf_model.html#R2">|=</a> <font color="Maroon">c<sub>2</sub></font> )
 ;<br/>


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