Do you have a citation for the "more creative in groups"? Some years ago I participated in a creativity/innovation course, and one of the things we were taught

Do you have a citation for the "more creative in groups"? Some years ago I participated in a creativity/innovation course, and one of the things we were taught was the brainstorming in groups had been found to be ineffective (because of group think, I think). I do agree that occasional chatting/communication is important otherwise, though, although I'm not really sure open plans foster that - seems to me to foster broadcasting rather than more productive one-on-one conversations.