https://dzone.com/articles/firebase-real-time-database-using-angular-4-ionic
origin - http://www.pipiscrew.com/2017/05/firebase-real-time-database-using-angular-4-and-ionic-3-2/ firebase-real-time-database-using-angular-4-and-ionic-3-2
https://dzone.com/articles/firebase-real-time-database-using-angular-4-ionic
origin - http://www.pipiscrew.com/2017/05/firebase-real-time-database-using-angular-4-and-ionic-3-2/ firebase-real-time-database-using-angular-4-and-ionic-3-2