Feedback cited as the core concept in Systems Dynamics

Cornell's SD site, in "Other Resources", at the bottom line, lists this:

The main concept behind system dynamics is feedback thinking. To explore the history of feedback thinking, see:

• Richardson, George P. (1991, 1999) Feedback Thought in Social Science and Systems Theory. Now available from Pegasus Communications (Click on the System Dynamics link in the “Browse Products by Subject box on the left-hand side.)