Leslie Garrett, Peter Greenberg: The Virtuous Consumer: Your Essential Shopping Guide for a Better, Kinder and Healthier World, New World Library, 2007, Seiten 17 bis 19, ISBN 1-930722-74-5.
Leslie Garrett, Peter Greenberg: The Virtuous Consumer: Your Essential Shopping Guide for a Better, Kinder and Healthier World, New World Library, 2007, Seiten 17 bis 19, ISBN 1-930722-74-5.