to avoid
             division by zero, be sure that the underground 
             input temperatures are non-zero and that the pressure 
             thicknesses of the underground layers are non-zero as well. 

==========================================================================

subroutine gcm_vert_diff_end

</PRE>
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<A NAME="CHANGES">
<HR>
<H4>CHANGE HISTORY</H4>
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<PRE>


<b>Chang