Echocardiographic Evidence of Aortopulmonary Collaterals in Premature Infants After Closure of Ductus Arteriosus - Birnbacher, Robert; Proll, E; Kohlhauser, Ch; Marx, M; Schlemmer, M; Dobner , M; Salzer-Muhar, U (American Journal of Perinatology, 1998)