Associations between reading achievement and independent reading in early elementary school: a genetically informative cross-lagged study.
Harlaar N, Deater-Deckard K, Thompson LA, Dethorne LS, Petrill SA. Associations between reading achievement and independent reading in early elementary school: a genetically informative cross-lagged study. Child Dev. 2011 Nov-Dec; 82(6):2123-37.