Several of us linguists at that time would record our own...

Several of us linguists at that time would record our own kids, just to get some data. There was some literature on it then, but no day-by-day, blow-by-blow examples. I recorded all my children over the years in some shape or form. It's what linguists do. You don't talk to a linguist without having what you say taken down and used in evidence against you at some point in time.