add backward typing rules

new_system3.tex

@@ -367,6 +367,8 @@ $x$ is supposed to be included into $t_x$ or $\neg t_x$.
 
 TODO: Improve Abs rule
 
+TODO: Is the Inter rule even needed?? (now that result of backtyping must be intersected with the original env)
+
 TODO: Algorithmic App, Inter and EFQ rule
 
 TODO: Is the Comp rule needed in this new setting where every application is alone in a let,