Is the pencil underrated? Tim Harford examines the role pencils have played in developing our world, and finds out why some writers have called them a "miracle of the free market". Do they have a point?
Henry Petroski - The Pencil: A History of Design and Circumstance, Faber and Faber London 1989
Milton Friedman, Free to Choose, PBS 1980
Eric Voice "History of the Manufacture of Pencils" 1950 Transactions of the Newcomen Society