anchor.diff:    placing it in the `<ng-content>` slot of the `HeroBioComponent` template:
   +makeExample('cb-dependency-injection/ts/app/hero-bio.component.ts','template','app/hero-bio.component.ts (template)')(format='.')
   :marked
  -  It looks like this, with the heroe's telephone number from `HeroContactComponent` projected above the hero description:
  +  It looks like this, with the hero's telephone number from `HeroContactComponent` projected above the hero description:
   figure.image-display
     img(src="/resources/images/cookbooks/dependency-injection/hero-bio-and-content.png" alt="bio and contact")    
   :marked
  
positive.code:   
    Where did the injector get that value?
    It may already have that value in its internal container. 
    It it doesn't, it may be able to make one with the help of a ***provider***.
    A *provider* is a recipe for delivering a service associated with a *token*.
  .l-sub-section
    :marked
  
negative.code:   
    Accordingly, dependencies provided in the root `AppComponent` can be injected into *any* component *anywhere* in the application.
    
    That isn't always desirable. 
    Sometimes we want to restrict service availability to a particular region of the application.
    
    We can limit the scope of an injected service to a *branch* of the application hierarchy
  