Sia is just a **** songwriter when it comes to other artists, well not fully ****, maybe 1/4 ****. It's like she half writes in a perspective similar to the artist she is writing for, and half in her own style. I enjoy most of her credits on other artists, but none of them are amazing or anything. I adore her solo material though.
Carly is just a great pop writer though, probably one of the best at the moment. I'm sure she could at least influence Sia abit in a positive way.
Moving on though, I wish the definition was on the back of the cover. Looks clunky on the front.