FreeCAD 0.15 (4671) : Sheet Metal Manual
(Manual) (日本語マニュアル)
https://www.dropbox.com/s/539nnfh9v6bb5q9/Free%20CAD%20%20Sheet%20Metal.pdf?dl=0
(Sheet metal Addon for FreeCAD)
https://theseger.com/projects/2015/06/sheet-metal-addon-for-freecad/
(FreeCAD_SheetMetal)
https://github.com/shaise/FreeCAD_SheetMetal
(Linux for an engineer)
https://linuxforanengineer.blogspot.com.es/2015/06/freecad-sheet-metal-update-2.html