"Patch's Propeller", Scientific America, vol. 4, no. 5, p. 33, October 10, 1848, archived from the original on July 8, 2011, retrieved 31 January 2010 – via The Archimedes Screw
US 5484264, Karls, Michael & Lindgren, Daniel, "Torsionally twisting propeller drive sleeve and adapter", published 1994-03-08, issued January 16, 1996
"Industry Pays Tribute to Innovation Awards Winners" Marine link, 3 October 2002. Accessed: 15 March 2014. Quote: "Winner: the energy-saving Kappel propeller concept from the European Commission-funded Kapriccio propulsion research project. Blades curved towards the tips on the suction side reduce energy losses, fuel consumption, noise and vibration"
"Patch's Propeller", Scientific America, vol. 4, no. 5, p. 33, October 10, 1848, archived from the original on July 8, 2011, retrieved 31 January 2010 – via The Archimedes Screw