ELhak, S. A. G., Ghanem, A. A. A., AbdelGhaffar, H., Dakroury, S. E., & Salama, M. M. (2010). Parkinson’s Disease: Is It a Toxic Syndrome?. Neurology Research International, 2010(), 2-11. https://doi.org/10.1155/2010/103094
Shen, K. M. (1981). An exploration into psychogenic pain and depression [master's thesis, The University of Hong Kong]. Airiti Library. https://www.airitilibrary.com/Article/Detail?DocID=U0029-1812201200004099
Sommer, S., Becher, B. A., & Jost, W. (2011). Nondipping in Parkinson’s Disease. Parkinson's Disease, 2011(), 821-825. https://doi.org/10.4061/2011/897586