| page.title=Building Apps with Contacts & Sign-In | |
| page.trainingcourse=true | |
| @jd:body | |
| <p>These lessons teach you how to include contact information and authenticate users with the same | |
| credentials they use for Google. These features allow your app to connect users with people they | |
| care about and provide a personalized experience without creating new user accounts.</p> |