Discoveries of Nicotinamide Riboside as a Nutrient and Conserved NRK Genes Establish a Preiss-Handler Independent Route to NAD+ in Fungi and Humans Bieganowski, Pawel et al. Cell , Volume 117, Issue 4 , 495 - 502. DOI: http://dx.doi.org/10.1016/S0092-8674(04)00416-7