When learning a new programming language it's desirable to write down its syntax for if you can't remember, for example, how to declare a class, you can always take a peek at your notes and remind yourself of the keywords that will make it happen.
After writing a few notes, they will need to be organized into groups, for if they aren't, it will be hard to quickly find related syntactic notes. A piece of paper on which these notes are organised are commonly known as a cheatsheet or reference sheet.
Every programming language, from C to Python and beyond has a cheatsheet and they are all different depending on which person designed them and for what purpose. Some cheatsheets are aimed at language learners; these cheatsheets have lots of comments that explain what are the consequences of using a statement and omit complicated syntactic features. Some cheatsheets are aimed at proficient users; these cheatsheets rarely have comments as they try to fit as many syntactic notes as possible onto a single piece of paper, for such users already know what are the consequences of invoking a statement, they just need to remind themselves of the proper statement syntax.
During the process of learning ABAP, I've noticed a distinct lack of ABAP cheatsheets of the Internet, especially those aimed at proficient users, so I've written my own ABAP cheatsheet.
The first page is complete and is an example of how I want the other pages to look like. It is dense: every line is filled with characters and there are 6,8 characters per square centimeter. Similar syntax is close to each other: class declaration near data declaration, internal tables near OpenSQL.
The other pages have room for additional notes and are not complete, which is part of the reason why I'm publishing the cheatsheet. I'd like to hear your feedback on how I can improve the cheatsheet: what notes should be on there and how can I write the syntax more concisely. My email address can be found at the bottom of the cheatsheet.