Fortino Morales Gutiérrez, Mario. La industria de la construcción y la infraestructura 2005-2015.México: Instituto Politécnico Nacional, 2007. p 58http://site.ebrary.com/lib/biblioucaucasp/Doc?id=10431029&ppg=58Copyright © 2007. Instituto Politécnico Nacional. All rights Reserved.May not be reproduced in any form without permission from the publisher, except fair uses permitted under U.S. or applicable copyright law.

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