Intracluster correlation coefficients for the Brazilian Multicenter Study on Preterm Birth (EMIP): methodological and practical implications - Lajos, Giuliane J.; Haddad, Samira M.; Tedesco, Ricardo P.; Passini Júnior, Renato; Dias, Tabata Z.; Nomura, Marcelo L.; Rheder, Patrícia M.; Sousa, Maria H.; Cecatti, José G.; Martinez, Francisco Eulogio (BMC Medical Research Methodology, 2014)