Motor learning, retention and transfer after virtual-reality-based training in Parkinson's disease – effect of motor and cognitive demands of games: a longitudinal, controlled clinical study - Mendes, Felipe Augusto dos Santos; Pompeu, José Eduardo; Lobo, Alexandra Modenesi; Silva, Keyte Guedes da; Oliveira, Tatiana keyte; Zomignani, Andrea Peterson; Piemonte, Maria Elisa Pimentel (Physiotherapy, 2012)