Charles (Business Improvement Group, LLC., Towson, Maryland, USA) Protzman & Mark Stevenson 
Card-Based Control Systems for a Lean Work Design 
The Fundamentals of Kanban, ConWIP, POLCA, and COBACABANA

Many shops have simplified their production control by using card-based systems such as kanban and Constant Work-in-Process (Con WIP). Although these systems provide a simple and highly effective visual approach for controlling manufacturing and service operations, all too many shops struggle with failed implementations or achieve results that fall