There are many and they seem to be coming at a furious pace, it is hard to keep up with them. However thanks to Paul D. Anderson, you can go to one spot to find out about each one of them.
I could sit here and opine about how/who/what, but that does really no good. There are too many questions, one that should not be overlooked is if/when the research was caught up enough to make proper safety information available to the players.
Here is the website, titled NFL Concussion Litigation. You can also follow Paul @PaulD_Anderson.
The Concussion Blog 