Cahyaningtyas, N. A., A. Sudiyanto, and R. Soemanto. “Socioeconomic Determinants of Healthy Ageing and the Contextual Effect of Peer Group: A Multilevel Evidence from Blora, Central Java”. Journal of Epidemiology and Public Health, vol. 4, no. 1, Jan. 2018, pp. 30-36, https://jepublichealth.com/index.php/jepublichealth/article/view/98.