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<b>let </b><font color="Maroon">H</font> be   <a href="zf_lang.html#NM2">ZF-formula</a>;<br/>

<b>assume </b><a NAME="E1:93"/>
<font color="Maroon">H</font> is <a href="zf_lang.html#V5" target="_self">conjunctive</a>
 ;<br/>

<a NAME="E2:93"/><b>then </b>
(  <a href="zf_lang.html#K21" target="_self">the_left_argument_of</a> <font color="Maroon">H</font> <a href="zf_lang.html#R1" target="_self">is_immediate_constituent_of</a> <font color="Maroon">H</font> &amp;  <a href="zf_lang.html#K22" target="_self">the_right_argument_of</a> <font color="Maroon">H</font> <a href="zf_lang.html#R1" target="_self">is_immediate_constituent_of</a> <font color="Maroon">H</font> )
 
<b>by </b><i><a class="ref" href="zf_lang.html#D10" target="_self">Def10</a></i>;<br/>
<b>hence </b><a NAME="E3:93"/>
(  <a href="zf_lang.html#K21" target="_self">the_left_argument_of</a> <font color="Maroon">H</font> <a href="zf_lang.html#R3" target="_self">is_proper_subformula_of</a> <font color="Maroon">H</font> &amp;  <a href="zf_lang.html#K22" target="_self">the_right_argument_of</a> <font color="Maroon">H</font> <a href="zf_lang.html#R3" target="_self">is_proper_subformula_of</a> <font color="Maroon">H</font> )
 <b>by </b><i><a class="ref" href="zf_lang.html#D20" target="_self">Def20</a></i>;<br/>


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