German sociologist Niklas Luhmann. One thing you should know about Luhmann—he was extremely productive. In his 40 years of research, he published more than 70 books and 500 scholarly articles. How did he do accomplish this? He credits it to his Zettelkasten which focuses on connections between notes.
To be super productive, Niklas Luhmann used to take notes relating to each other





















and one more:




