Sackley, C. M., Smith, C. H., Rick, C., Brady, M. C., Ives, N., Patel, R., Roberts, H., Dowling, F., Jowett, S., Wheatley, K., Patel, S., Kelly, D., Sands, G., & Clarke, C. (2014). Lee Silverman voice treatment versus standard NHS speech and language therapy versus control in Parkinson's disease (PD COMM pilot): study protocol for a randomized controlled trial. Trials, 15, Article 213. https://doi.org/10.1186/1745-6215-15-213