Fix docs links

content/lesson/6.md

@@ -340,7 +340,7 @@ But let's return to using normal-ish instructions instead of changing the way la
 Instead of just one `phi` instruction, let's introduce two new instructions: `set` and `get`.
 (These are called `upsilon` and `phi` in [Pizlo's sketch][pizlo], but I've renamed them for clarity.)
 The semantics of these instructions will read and write from *shadow variables* that exist in a separate environment from the "normal" variables in a function.
-Critically, these shadow variables can violate the core SSA restriction: they can have multiple writers, in the same way that classic ϕ-nodes can get their values from multiple predecessors.
+Critically, these shadow variables do not obey the SSA restriction that applies to regular variables: they can have multiple writers, in the same way that classic ϕ-nodes can get their values from multiple predecessors.
 
 The `set` instruction looks like this:
 
@@ -397,7 +397,7 @@ Beyond that, SSA form is just a restriction on the normal expressiveness of Bril
 
 The [reference interpreter][brili] has built-in support for `set` and `get`, so you can execute your SSA-form Bril programs without fuss.
 
-[bril-ssa2]: https://capra.cs.cornell.edu/bril/lang/ssa.html
+[bril-ssa2]: https://capra.cs.cornell.edu/bril/lang/ssa2.html
 [brili]: https://capra.cs.cornell.edu/bril/tools/interp.html