This International Standard specifies strength test conditions and requirements for the 40 mm and 50 mm drawbar couplings and corresponding drawbar eyes for hinged drawbars. This title may contain less than 24 pages of technical content.
You can specify the type of files you want, for your gadget.ISO 8718:2001, Road vehicles - Drawbar couplings and eyes for hinged drawbars - Strength tests | ISO/TC 22/SC 15. I was recommended this book by a dear friend of mine.