[GCM] android reference

【Android】使用 GCM(Google Cloud Messaging)
http://oldgrayduck.blogspot.tw/2012/11/android-gcmgoogle-cloud-messaging.html

【Android】Cloud Messaging Api(GCM) 使用
http://anson-programming.blogspot.tw/2015/08/android-gcm.html
https://bitbucket.org/ct7ct7ct7/demo-android_pushtest/downloads

Android Push Notifications using Google Cloud Messaging GCM - Android Example
http://androidexample.com/Android_Push_Notifications_using_Google_Cloud_Messaging_GCM/index.php?view=article_discription&aid=119&aaid=139

Engage your users across Android, iOS and Chrome
https://developers.google.com/cloud-messaging/