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<div><span class="kw">theorem </span><a NAME="T19"><span class="comment"><font color="firebrick">:: VALUED_0:19</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">XX</font> being   non  <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>   <a href="hidden.html#M2" title="HIDDEN:mode.2">set</a> <br/>  for <font color="Olive" title="b2">ss</font> being   <a href="nat_1.html#NM1" title="NAT_1:NM.1">sequence</a> of <font color="Olive" title="b1">XX</font> holds  <font color="Olive" title="b2">ss</font> is    <a href="valued_0.html#M2" title="VALUED_0:mode.2">subsequence</a> of <font color="Olive" title="b2">ss</font></div></div>
