Brusov, P., T. Filatova, N. Orekhova, and V. Kulik. “Rating Methodology: New Look and New Horizons”. Journal of Reviews on Global Economics, vol. 7, Mar. 2018, pp. 63-87, https://mail.lifescienceglobal.com/pms/index.php/jrge/article/view/5277.