# This book is not accepted in AUT-QE because [y:'type'] is not allowed
# This book is accepted in lambda-delta with sort inclusion but Omega is not
# valid if sort inclusion is allowed on the term backbone only
-# This book is valid in lambda-delta with sort inclusion allowed everywhere
+# This book is valid in lambda-delta with unrestricted sort inclusion
+l
@ Delta := [x:[y:'type']'type']<x>x : [x:[y:'type']'type']'type'