I've posted a series of articles for the R1b project members as background in preparation for this.
Those articles include topics like, PIE, Yamnaya, Corded Ware, Single Grave CW, Bell Beakers, P312 distribution, U106 distribution, Z2103 distribution, etc.

This graphic is intended as a visual to discuss L51 and its descendants. It's too busy as it is so I'm trying not to add more detail but I definitely want to correct errors. Feedback?