Pelupessy, J. M., Radianah Makmur, and Dasril Daud. 1991. “Bull-Neck, Electrocardiographic Changes and Creatine Phosphokinase Blood Levels in Patients With Diphtheria”. Paediatrica Indonesiana 31 (11-12), 303-11. https://paediatricaindonesiana.org/index.php/paediatrica-indonesiana/article/view/1452.