Toyota took all of the good ideas they found in American companies (most specifically Ford) in the 1950s and added continuous improvement. Then they actually iterated with continuous improvement.
So I don't think it's fair to say that any of the ideas are outright stolen (I know you didn't say that either), because Toyota took them well past the starting point.
I've read it mentioned a number of places - as it's somewhat mythical - but the source that comes to mind at the moment - but perhaps I'm getting it wrong? - was the book "Creativity Inc."
