Lungu C, Nmashie A, George MC, Karp BI, Alter K, Shin S, Tse W, Frucht SJ, Wu T, Koo V, Considine E, Norato G, Hallett M, Simpson DM. Comparison of Ultrasound and Electrical Stimulation Guidance for Onabotulinum Toxin-A Injections: A Randomized Crossover Study. Mov Disord Clin Pract. 2022 Nov; 9(8):1055-1061.