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Engstrand, Iris H.W. (Fall 2014). "WD-40: San Diego's Marketing Miracle"(PDF). The Journal of San Diego History. 60 (4): 253–270. Archived(PDF) from the original on December 22, 2015. Retrieved March 7, 2017.
Engstrand, Iris H.W. (Fall 2014). "WD-40: San Diego's Marketing Miracle"(PDF). The Journal of San Diego History. 60 (4): 253–270. Archived(PDF) from the original on December 22, 2015. Retrieved March 7, 2017.