diff --git a/examples/addressbook.proto b/examples/addressbook.proto
index bfdceea..23cc2f9 100644
--- a/examples/addressbook.proto
+++ b/examples/addressbook.proto
@@ -1,16 +1,29 @@
 // See README.txt for information and build instructions.
+//
+// Note: START and END tags are used in comments to define sections used in
+// tutorials.  They are not part of the syntax for Protocol Buffers.
+//
+// To get an in-depth walkthrough of this file and the related examples, see:
+// https://developers.google.com/protocol-buffers/docs/tutorials
 
+// [START declaration]
 syntax = "proto3";
-
 package tutorial;
+// [END declaration]
 
+// [START java_declaration]
 option java_package = "com.example.tutorial";
 option java_outer_classname = "AddressBookProtos";
-option csharp_namespace = "Google.Protobuf.Examples.AddressBook";
+// [END java_declaration]
 
+// [START csharp_declaration]
+option csharp_namespace = "Google.Protobuf.Examples.AddressBook";
+// [END csharp_declaration]
+
+// [START messages]
 message Person {
   string name = 1;
-  int32 id = 2;        // Unique ID number for this person.
+  int32 id = 2;  // Unique ID number for this person.
   string email = 3;
 
   enum PhoneType {
@@ -31,3 +44,4 @@
 message AddressBook {
   repeated Person people = 1;
 }
+// [END messages]