DiBenedetti DB, Price MA, Andrews EB. Cognitive interviewing in risk minimization survey development: patient and healthcare professional surveys. Expert Rev Clin Pharmacol. 2013;6(4):369-73.
Fleming AD, Xia X, McDicken WN, Sutherland GR, Fenn L. Myocardial velocity gradients detected by Doppler imaging. Br J Radiol. 1994 Jul 1;67(799):679-88. doi: 10.1259/0007-1285-67-799-679