| https://d.android.com/guide/components/activities/activity-lifecycle |
| https://developer.android.com/guide/components/activities/state-changes |
| https://developer.android.com/guide/components/activities/testing |
| https://developer.android.com/guide/components/activities/tasks-and-back-stack |
| https://developer.android.com/guide/components/activities/recents |
| https://d.android.com/guide/components/activities/background-starts |