Surat na di Toru
c Ida ma The Journal of Thoracic and Cardiovascular Surgery, Volume 89, No. 6, alm. 918; dohot Heart, Lung and Circulation, Volume 19, alm. 658.
c Ida ma The Journal of Thoracic and Cardiovascular Surgery, Volume 89, No. 6, alm. 918; dohot Heart, Lung and Circulation, Volume 19, alm. 658.