<?xml version="1.0"?>
<div class="add">

<b>let </b><font color="Maroon">W</font> be   <a href="classes2.html#NM1">Universe</a>;<br/><b>let </b><font color="Maroon">a</font> be    <a href="ordinal4.html#M1">Ordinal</a> of <font color="Maroon">W</font>;<br/>



<b>assume </b><a NAME="E1:44"/>
 <a href="ordinal1.html#K5">omega</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">W</font>
 ;<br/>

<b>then consider </b><font color="Maroon">b</font> being    <a href="ordinal4.html#M1">Ordinal</a> of <font color="Maroon">W</font>, <font color="Maroon">M</font> being  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E3:44"/><i><font color="Green">E37</font></i>: 
( <font color="Maroon">a</font> <a href="hidden.html#R2">in</a> <font color="Maroon">b</font> &amp; <font color="Maroon">M</font> <a href="hidden.html#R1">=</a>  <a href="classes1.html#K4">Rank</a> <font color="Maroon">b</font> &amp; <font color="Maroon">M</font> <a href="zfrefle1.html#R3" target="_self">is_elementary_subsystem_of</a> <font color="Maroon">W</font> )
 <b>by </b><i/>;<br/>
<b>take </b>
<font color="Maroon">b</font>
;<br/>

<b>take </b>
<font color="Maroon">M</font>
;<br/>

<b>thus </b><a NAME="E4:44"/>
( <font color="Maroon">a</font> <a href="hidden.html#R2">in</a> <font color="Maroon">b</font> &amp; <font color="Maroon">M</font> <a href="hidden.html#R1">=</a>  <a href="classes1.html#K4">Rank</a> <font color="Maroon">b</font> &amp; <font color="Maroon">M</font> <a href="zfrefle1.html#R2" target="_self">&lt;==&gt;</a> <font color="Maroon">W</font> )
 <b>by </b><i>, </i>;<br/>


</div>
