1) http://exploration.grc.nasa.gov/education/rocket/newton3r.html

2) http://www.physchem.co.za/Motion/Third%20Law.htm

3) http://physics.nmt.edu/~raymond/classes/ph13xbook/node104.html

4)http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html