= Firebase =
 * https://firebase.google.com/
 * https://en.wikipedia.org/wiki/Firebase
Firebase is a platform developed by Google for creating mobile and web applications.

== Cloud messaging ==
 * https://firebase.google.com/products/cloud-messaging
 * https://firebase.google.com/docs/cloud-messaging
 * https://console.firebase.google.com/project/_/notification
 * https://console.firebase.google.com/project/bitarus-sandbox-fcm/notification