• Background/motivation from David Gordon Wilson. "CPSC Proposals", HPV mailing list, 2005/05/22.
• Background/motivation from David Gordon Wilson. HPV digest V2 #175, 1995/03/29.
• Positech, in "The Brake That Got Away" (D.G. Wilson), Velo Vision 3 Sep 2001, p16 http://www.velovision.co.uk Velo Vision web site (2006/07).
• Wilson/Hanson/Malarkey patent 1972: US003870127.1.tiff, US003870127.2.tiff, US003870127.3.tiff, US003870127.4.tiff, US003870127.5.tiff
• Amrstrong patent, 1975: US004015690.1.tiff, US004015690.2.tiff, US004015690.3.tiff, US004015690.4.tiff, US004015690.5.tiff, US004015690.6.tiff, US004015690.7.tiff
• Both patents, as a PDF.