ASHRAE Journal, Nov. 2016, by Armin Hauer.
http://bookstore.ashrae.biz/journal/download.php?file=2016Nov_052-059_Hauer.pdf

"Highly efficient air systems require precise fan selection and a method to adjust the fan performance to the Load. Fan supplier applications engineers are experienced in identifying the most suitable fan type and fan size for a specified application, whether the fan duty is fixed or continuously variable. Manufacturer-certified performance and electrical power consumption data support competitive performance contracts and ensure minimum energy consumption."