Ebeling Barbier C., Johansson L., Lind L., Ahlström H., and Bjerner T. “Several Sources of Error in Estimation of Left Ventricular Mass With M-Mode Echocardiography in Elderly Subjects”. Upsala Journal of Medical Sciences, vol. 116, no. 4, Nov. 2011, pp. 258–264, doi:10.3109/03009734.2011.596586.