Journal of AOAC International, Volume 95, Number 5, September/October 2012 , pp. 1479-1486(8),Simultaneous Determination of Free Carnitine and Total Choline by Liquid Chromatography/Mass Spectrometry in Infant Formula and Health-Care Products: Single-Laboratory Validationhttp://aoac.publisher.ingentaconnect.com/content/aoac/jaoac/2008/00000091/00000004/art00013