http://www.bondioli-pavesi.com/particolareProdotti.jsp?catID=1122
http://www.ruukki.com/www/materials.nsf/materials/8F1807C9D24BAA3AC2257236003D1A63/$File/Optim%20HS%20500%20MH_TP_08.2005_FI.pdf?openElement
http://tractortestlab.unl.edu/NewH/NH%20TM_190.pdf