- https://firebase.googleblog.com/2017/03/how-to-schedule-cron-jobs-with-cloud.html
- https://github.com/firebase/functions-samples/tree/master/delete-unused-accounts-cron
- https://www.youtube.com/watch?v=CbE2PzvAMxA
- https://github.com/firebase/functions-samples/tree/master/quickstarts/email-users
- https://github.com/firebase/functions-samples/tree/master/email-confirmation
- https://medium.com/@markgoho/create-a-contact-form-in-angular-using-cloud-functions-for-firebase-5e390bdf5600
- https://cloud.google.com/functions/docs/tutorials/sendgrid
- https://www.mailjet.com/google
- http://www.mailgun.com/google
- https://www.youtube.com/watch?v=RdqV_N0sCpM
- https://www.youtube.com/watch?v=SnWwkURpwxs
- https://www.youtube.com/watch?v=G-MBeEW92v4
- https://github.com/Polymer/hn-polymer-2/tree/master/functions
- https://saythat.io
- https://github.com/laurenzlong/say-that
- https://github.com/firebase/say-that
- https://firesale.fyi