Selection bias and patterns of confounding in cohort studies: the case of the NINFEA web-based birth cohort
Costanza Pizzi, Bianca L De Stavola, Neil Pearce, Fulvio Lazzarato, Paola Ghiotti, Franco Merletti, Lorenzo Richiardi
J Epidemiol Community Health Nov 2012, 66 (11) 976-981; DOI: 10.1136/jech-2011-200065