IF YOU CAN SEE THIS go to http://www.cs.cornell.edu/Info/People/sfa/Nuprl/Shared/Xindentation_hack_doc.html
At:
iseg is sublist T:Type, L_1,L_2:T List. L_1L_2L_1L_2
By:
Unfold `sublist` 0
THEN
Inst Thm*l1,l2:T List. l1l2 ||l1||||l2|| [T;L_1;L_2]
THEN
Inst
Thm*l1,l2:T List. l1l2 ||l1||||l2|| & (i:. i<||l1|| l1[i] = l2[i])
[T;L_1;L_2]
THEN
InstConcl [i.i]
THEN
Reduce 0
THEN
Try (BackThru Thm*k:. increasing(i.i;k))