Here are the first versions of the Reference Sheets, sometimes the are also called cheatsheets, These Reference Sheets are a concise set of notes used for quick reference.
In more general usage, a Reference Sheets is any short (one- or two-page) reference to terms, commands, or symbols where the user is expected to understand the use of such terms but not necessarily to have memorized all of them. Many computer applications, for example, have these Sheets included in their documentation, which list keystrokes or menu commands needed to achieve specific tasks to save the user the effort of digging through an entire manual to find the keystroke needed to, for example, move between two windows. An example of such a Sheets is a “Quick Reference Card” documents included with consumer electronics.
Some academic and technical publishers also publish Reference Sheets for software packages and technical topics. In some cases these are also intended as display items in that they are colorful and visually appealing. Web-based Sheets, such as references to terms, commands, or symbols, have become extremely common. These are meant to be used as quick reference guides for any electronic / electrical project. I have made these Sheets in A5 format for easy use.