V. . Poomlek, W. . Chaitree, P. . Thongcharoen, P. Panchavinnin, and N. . Opartkiattikul, “A Comparative Study of Portable Monitors (CoaguCheck®XS) for International Normalized Ratio (INR)”, Siriraj Med J, vol. 60, no. 1, pp. 10–13, Jan. 2008.