diff --git a/interfaces/11-sort/list.go b/interfaces/11-sort/list.go
index 722b337..2e12a89 100644
--- a/interfaces/11-sort/list.go
+++ b/interfaces/11-sort/list.go
@@ -65,5 +65,5 @@ func (bp byRelease) Swap(i, j int) { bp.list.Swap(i, j)   }
 */
 
 func byReleaseDate(l list) sort.Interface {
-	return &byRelease{l}
+	return byRelease{l}
 }
diff --git a/interfaces/11-sort/main.go b/interfaces/11-sort/main.go
index 1ebb40d..fd47fb5 100644
--- a/interfaces/11-sort/main.go
+++ b/interfaces/11-sort/main.go
@@ -9,6 +9,7 @@ package main
 
 import (
 	"fmt"
+	"sort"
 )
 
 func main() {
@@ -18,10 +19,10 @@ func main() {
 		{title: "hobbit", price: 25},
 	}
 
-	// sort.Sort(l)
-	// sort.Sort(sort.Reverse(l))
-	// sort.Sort(byReleaseDate(l))
-	// sort.Sort(sort.Reverse(byReleaseDate(l)))
+	sort.Sort(l)
+	sort.Sort(sort.Reverse(l))
+	sort.Sort(byReleaseDate(l))
+	sort.Sort(sort.Reverse(byReleaseDate(l)))
 
 	fmt.Print(l)
 }
@@ -33,13 +34,14 @@ Summary:
 
 - sort.Interface has three methods: Len(), Less(), Swap()
   - Len() returns the length of a collection.
-  - Less() should return true when an element comes before another one.
-  - Swap()s the elements when Less() returns true.
+  - Less(i, j) should return true when an element comes before another one.
+  - Swap(i, j)s the elements when Less() returns true.
 
-- sort.Reverse() sorts a sort.Interface value.
+- sort.Reverse() can reverse sort a type that satisfies the sort.Interface.
 
 - You can customize the sorting:
-  - by anonymously embedding the sort.Interface type
+  - Either by implementing the sort.Interface methods,
+  - or by anonymously embedding a type that already satisfies the sort.Interface
   - and adding a Less() method.
 
 - Anonymous embedding means auto-forwarding method calls to an embedded value.
diff --git a/interfaces/12-marshaler/list.go b/interfaces/12-marshaler/list.go
index e313b8f..8b09119 100644
--- a/interfaces/12-marshaler/list.go
+++ b/interfaces/12-marshaler/list.go
@@ -50,5 +50,5 @@ func (bp byRelease) Less(i, j int) bool {
 }
 
 func byReleaseDate(l list) sort.Interface {
-	return &byRelease{l}
+	return byRelease{l}
 }
diff --git a/interfaces/12-marshaler/main.go b/interfaces/12-marshaler/main.go
index a238fd9..1451b43 100644
--- a/interfaces/12-marshaler/main.go
+++ b/interfaces/12-marshaler/main.go
@@ -34,14 +34,12 @@ func main() {
 Summary:
 
 - json.Marshal() and json.MarshalIndent() can only encode primitive types.
-  - It cannot encode custom types.
-  - Implement the json.Marshaler interface and teach it how to encode your custom types.
-  - See time.Time code: It satisfies the json.Marshaler interface.
+  - Custom types can tell the encoder how to encode.
+  - To do that satisfy the json.Marshaler interface.
 
 - json.Unmarshal() can only decode primitive types.
-  - It cannot decode custom types.
-  - Implement the json.Unmarshaler interface and teach it how to decode your custom types.
-  - See time.Time code: It satisfies the json.Unmarshaler interface as well.
+  - Custom types can tell the decoder how to decode.
+  - To do that satisfy the json.Unmarshaler interface.
 
 - strconv.AppendInt() can append an int value to a []byte.
   - There are several other functions in the strconv package for other primitive types as well.
diff --git a/interfaces/13-io/list.go b/interfaces/13-io/list.go
index 94f5c04..fa60a0f 100644
--- a/interfaces/13-io/list.go
+++ b/interfaces/13-io/list.go
@@ -50,5 +50,5 @@ func (bp byRelease) Less(i, j int) bool {
 }
 
 func byReleaseDate(l list) sort.Interface {
-	return &byRelease{l}
+	return byRelease{l}
 }
diff --git a/interfaces/14-composition/list.go b/interfaces/14-composition/list.go
index 94f5c04..fa60a0f 100644
--- a/interfaces/14-composition/list.go
+++ b/interfaces/14-composition/list.go
@@ -50,5 +50,5 @@ func (bp byRelease) Less(i, j int) bool {
 }
 
 func byReleaseDate(l list) sort.Interface {
-	return &byRelease{l}
+	return byRelease{l}
 }