Poehling KA, Fairbrother G, Zhu Y, Donauer S, Ambrose S, Edwards KM, Staat MA, Prill MM, Finelli L, Allred NJ, Bardenheier B, Szilagyi PG. Practice and child characteristics associated with influenza vaccine uptake in young children. Pediatrics. 2010 Oct; 126(4):665-73.