Package structure - mgolokhov/dodroid GitHub Wiki

https://guides.codepath.com/android/Organizing-your-Source-Files#organize-packages-by-category

https://github.com/futurice/android-best-practices#java-packages-architecture

https://medium.com/@cesarmcferreira/package-by-features-not-layers-2d076df1964d#.gyui6v7tw

http://www.therealjoshua.com/2011/11/android-architecture-part-2-packages/

https://codelabs.developers.google.com/codelabs/android-testing/index.html?index=..%2F..%2Fbabbq-2015&viewga=%20UA-68632703-1#4

https://www.linkedin.com/pulse/android-package-structure-performance-tam-nguyen

http://blog.smartlogic.io/2013/07/09/organizing-your-android-development-code-structure