diff --git a/src/ch04/s00-concerns.md b/src/ch04/s00-concerns.md
index 13b9c95..fc56360 100644
--- a/src/ch04/s00-concerns.md
+++ b/src/ch04/s00-concerns.md
@@ -3,13 +3,13 @@
 ## There exist alternative `Functor` implementations
 See the [relevant subchapter](./s01-alternatives.md)
 
-## It might be better to have a per-lifetime trait for `Functor`s
+## ~~It might be better to have a per-lifetime trait for `Functor`s~~ done
 See the [relevant subchapter](./s02-lifetimes.md)
 
 ## `Stackless` is kind of bad
 See the [relevant subchapter](./s03-stackless.md)
 
-## `WeakFunctor::F<'a, A>` is not (yet) covariant over the lifetime `'a`
+## `WeakFunctor<'a>` is not (yet) covariant over the lifetime `'a`
 See the [relevant subchapter](./s04-covariance.md)
 
 ## `Fail`/`FailMonad`/etc. have unclear semantics
diff --git a/src/ch04/s01-alternatives.md b/src/ch04/s01-alternatives.md
index 735e65b..29a200d 100644
--- a/src/ch04/s01-alternatives.md
+++ b/src/ch04/s01-alternatives.md
@@ -6,10 +6,8 @@ Copied for reference. All following examples are in the same `Functor`-`Applicat
 without extra (sub)traits like `WeakFunctor`, `Pure`, `ApplicativeLA2`, etc. .
 
 ```rust
-trait Functor {
-    type F<'a, A: 'a>: 'a
-    where
-        Self: 'a;
+trait Functor<'a>: 'a {
+    type F<A: 'a>: 'a;
 
     fn fmap<'a, A: 'a, B: 'a>(
         f: impl 'a + FnOnce(A) -> B, fa: Self::F<'a, A>,
diff --git a/src/ch04/s02-lifetimes.md b/src/ch04/s02-lifetimes.md
index 0ff255b..8b97d27 100644
--- a/src/ch04/s02-lifetimes.md
+++ b/src/ch04/s02-lifetimes.md
@@ -2,17 +2,13 @@
 
 Current:
 ```rust
+pub trait WeakFunctorA<'a>: 'a {
+    type F<A: 'a>: 'a;
+}
+
 pub trait WeakFunctor {
     type F<'a, A: 'a>: 'a
     where
         Self: 'a;
 }
 ```
-
-Proposed:
-```rust
-pub trait WeakFunctor<'a>: 'a {
-    type F<A: 'a>: 'a;
-}
-```
-
diff --git a/src/ch04/s04-covariance.md b/src/ch04/s04-covariance.md
index 0cb0c7a..46b62cc 100644
--- a/src/ch04/s04-covariance.md
+++ b/src/ch04/s04-covariance.md
@@ -1,4 +1,4 @@
-## `CovariantFunctor` not (yet) included in `Monad`
+**`CovariantFunctor` was deleted.**
 
 ## Specific case: `Stackless<'a>` isn't covariant