This link will take you to the CIPD page on change management:

https://www.cipd.co.uk/knowledge/strategy/change/management-factsheet

This link will take you to the ACAS page on change management:

http://www.acas.org.uk/index.aspx?articleid=4669

For more on Kurt Lewin see http://www.infed.org/thinkers/et-lewin.htm