Lumban Tobing, M. U. “The Effect Of Giving Exercise Of Passive Range Of Motion (ROM) To The Flexibility Of Knee Joint In Elderly: Subtitle : There Is the Effect Of Giving Exercise Of Passive Range Of Motion (ROM) To The Flexibility Of Knee Joint In Elderly”. Jurnal Kesehatan Ilmiah Indonesia / Indonesian Health Scientific Journal, vol. 4, no. 2, Dec. 2019, pp. 41-47, https://jurnal.unar.ac.id/index.php/health/article/view/61.