Sackley, C., Smith, C., Rick, C., Brady, M., Ives, N., Patel, S., … Collaborative, G. P. C. P. Lee Silverman Voice Treatment versus standard speech and language therapy versus control in Parkinson’s disease: a pilot randomised controlled trial (PD COMM pilot). Pilot and Feasibility Studies, 4, 30. https://doi.org/10.1186/s40814-017-0222-z (Original work published 2018)