Learning curves and training thresholds for paediatricians performing neonatal hip ultrasound using the Graf method in a universal screening program - Aguilar,I.M.; Marrón,L.F.; Gómez,M.P.; Herrera,C.G.; Olteanu,C.O.; Andreu,E.C.; Ruiz,C.L.; Bartolomé,A.A.; Matamala,A.O. (European Journal of Pediatrics, 2026)