Harimurti, G. M., and M. Munawar. “The Role of Transthoracal Echocardiography in Closing Secundum Atrial Septal Defects With Amplatzer Septal Occluder”. Medical Journal of Indonesia, Vol. 16, no. 1, Feb. 2007, pp. 14-8, doi:10.13181/mji.v16i1.251.