We all have certain friends that we know we can turn to when times get tough. For Katy Perry, that friend is Sia. Perry has praised the enigmatic Australian singer-songwriter in a new interview ...

the Max Martin- produced "Chained To the Rhythm" (also co-written by Sia) broke through at No. 4 on the Hot 100. As the introduction to "143," Perry's upcoming album set to arrive on Sept.