movie factory to add subtitles

https://www.youtube.com/watch?v=dadOkV5IZ_0

Gcse maths calculator that can use

http://www.examsolutions.net/calculators.php

Check whether a value exist in json

http://stackoverflow.com/questions/6384421/check-whether-a-value-exists-in-json-object

Defer load javascript

https://varvy.com/pagespeed/defer-loading-javascript.html

Javascript set time out

http://stackoverflow.com/questions/20256296/load-javascript-after-5-seconds-after-page-has-loaded

Iab plugin

https://www.npmjs.com/package/cordova-plugin-google-payments

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