Serum 25-hydroxyvitamin D levels among US children aged 1 to 11 years: do children need more vitamin D?
Mansbach JM, Ginde AA, Camargo CA. Serum 25-hydroxyvitamin D levels among US children aged 1 to 11 years: do children need more vitamin D? Pediatrics. 2009 Nov; 124(5):1404-10.