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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E57">Th68</font></span>: <a NAME="T68"><span class="comment"><font color="firebrick">:: ZF_LANG:68</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">x</font>, <font color="Olive" title="b2">y</font> being   <a href="zf_lang.html#NM1" title="ZF_LANG:NM.1">Variable</a><br/>  for <font color="Olive" title="b3">F</font> being   <a href="zf_lang.html#NM2" title="ZF_LANG:NM.2">ZF-formula</a>  holds  not <font color="Olive" title="b3">F</font> <a href="zf_lang.html#R3" title="ZF_LANG:pred.3">is_proper_subformula_of</a> <font color="Olive" title="b1">x</font> <a href="zf_lang.html#K4" title="ZF_LANG:func.4">'in'</a> <font color="Olive" title="b2">y</font></div></div>
