Use an iPad as a monitor for a Windows PC with Duet Display, the fastest way to add another monitor to your desktop or laptop.
How to Use iPad as Second Monitor for Windows
Best App for Using Your iPad as a Second Monitor or External Display
App of the Week: Duet Display turns an iPad into your Mac's second screen – GeekWire
Possible to use a ipad as a second monitor for another ipad? : r/ipad
Duet - Remote Desktop, Second Display, Drawing Tablet, and More
How to Use Your iPad as a Second Screen for Your PC or Mac
Duet Display Guide: How to set up a second screen - TapSmart
Dual Display: How to Use Your iPad as a Second Monitor on Any Computer
DUET The App That Turns Your iPad Into A Good Second Monitor
Duet - Remote Desktop, Second Display, Drawing Tablet, and More
This App Lets You Use an iPad as a Second PC Screen