IF YOU CAN SEE THIS go to http://www.cs.cornell.edu/Info/People/sfa/Nuprl/Shared/Xindentation_hack_doc.html
At:
hd l interval T:Type, l:T List, i:||l||, j:i. hd(l_interval(l;j;i)) = l[j]
By:
UnivCD THEN Subst (hd(l_interval(l;j;i)) ~ l_interval(l;j;i)[0]) 0