1. Maniwa, H., Kotani, K., Suzuki, S., Asao, T.: Influence in posture of the upper extremity through the use of various size of tablets and characters. J. Mob. Interact. 3(1), 33–38 (2013). (in Japanese)
2. How to use the Windows 10 touch keyboard. http://www.techradar.com/how-to/software/operating-systems/how-to-make-the-most-out-of-the-windows-10-touch-keyboard-1307508/2 . Accessed 18 Dec 2017
3. Basic operation of iPhone (keyboard chapter). http://iphoneac.com/beginner4.html , 18 Dec 2017
4. A.I. type Tablet Keyboard, https://play.google.com/store/apps/details?id=com.aitype.android.tablet . Accessed 18 Dec 2017
5. How to Undock & Split Your iPad Keyboard. http://www.macobserver.com/tmo/article/how-to-undock-and-split-your-ipad-keyboard . Accessed 18 Dec 2017