Avoid a possible variable name conflict in instantiating a theorem.
Instantiating a theorem variable with new variables created a possible
variable name conflict if a record was defined with a field named
'f', 'x' etc. Using variable indices of 1 avoids the problem.
use "../settings";
use_thy "termination";
use_thy "Induction";
use_thy "Nested1";
use_thy "Nested2";