Giorgio Derchi, Manuela Balocco, Patrizio Bina, Vincenzo Caruso, Domenico G D’Ascola, Roberto Littera, Raffaella Origa, Maria D. Cappellini, Gian L. Forni. Efficacy and safety of sildenafil for the treatment of severe pulmonary hypertension in patients with hemoglobinopathies: results from a long-term follow up. Haematologica 2014;99(2):e17-e18; https://doi.org/10.3324/haematol.2013.095810.