Siddiqui MS, Fernandez HH, Garvan CW, Kirsch-Darrow L, Bowers D, Rodriguez RL, Jacobson CE, Rosado C, Vaidyanathan S, Foote KD, Okun MS. Inappropriate crying and laughing in Parkinson disease and movement disorders. World J Biol Psychiatry. 2009; 10(3):234-40.