Woodward, WR, CW Olanow, RM Beckner, RA Hauser, LL Gauger, JM Cedarbaum, and J Nutt. 1993. “The Effect of L-Dopa Infusions With and Without Phenylalanine Challenges in Parkinsonian Patients: Plasma and Ventricular CSF L-Dopa Levels and Clinical Responses. Neurology 1993;43:1704-1708.”. Neurology.