message: books: update the link
diff: @@ -42,7 +42,8 @@ const omvDataSource = new harp.OmvDataSource({
  map.addDataSource(omvDataSource);
  ```
  -You need to [HERE Credentials](obtain authentication code) to replace 'YOUR-XYZ-TOKEN'.
  +You need to [obtain authentication code](#credentials) to replace 'YOUR-XYZ-TOKEN'.
  +
  For more information on the simple bundle, please visit the [@here/harp.gl module](../@here/harp.gl) directory.
  