Brian Clifton. Tracking Offline Marketing using Google Analytics. Version 1.1, September 2010. 13 p. URL: https://brianclifton.com/Tracking-Offline-Marketing.pdf.
Brian Clifton. Understanding Web Analytics Accuracy. Version 2.0, March 2010. 20 p. URL: https://brianclifton.com/pro-lounge-files/accuracy-whitepaper.pdf.