1. Capra, Fritjof, (1984) ‘Het Keerpunt’ (The Turning Point) ISBN 90-254-6918-3 Contact, Amsterdam
2. Margulis, Lynn, (1998) ‘Symbiotic Planet’ ISBN 0-46507271-2 Basic Books, New York
3. Johnson Johnson (2007) ‘Social Interdependence Theory’ (online) available from:
4. http://www.ceebl.manchester.ac.uk/events/archive/aligningcollaborativelearning/JohnsonJohnson.pdf
5. Campbell, Jeremy (1982) ‘Grammatical Man’ ISBN 067-1-44061-8, Simon Schuster, New York