The March feature on the La Nación office tower in Buenos Aires, Argentina ("Doubled up," p. 24) incorrectly stated that Nortel is based in Norway. The company is headquartered in Brampton, Ontario, Canada.
A website link cited in our February story on roofing design tips (p.48) has since changed. The new link to National Roofing Contractors Association's Roofing and Waterproofing Manual is: www.nrca.net/rp/technical/manual/03update.aspx.
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