Comparison of Smooth‐Gel Hyaluronic Acid Dermal Fillers with Cross‐linked Bovine Collagen: A Multicenter, Double‐Masked, Randomized, Within‐Subject Study - BAUMANN, LESLIE S.; SHAMBAN, AVA T.; LUPO, MARY P.; MONHEIT, GARY D.; THOMAS, JANE A.; MURPHY, DIANE K.; WALKER, PATRICIA S. (Dermatologic surgery, 2007)