Ali, M.A., Haque, A., Anwarulla, A. and Ahmad, Q. 2009. Non–motor Symptoms in Parkinson’s Disease: It’s Relationship with Age of Onset, Duration and Stage of Disease and the Dose and Duration of Levodopa Usage. TAJ: Journal of Teachers Association. 21, 1 (Sep. 2009), 12–17. DOI:https://doi.org/10.3329/taj.v21i1.3211.