In 1944, Warburg was nominated for a second Nobel Prize in Physiology by Albert Szent-Györgyi, for his work on nicotinamide, the mechanism and enzymes involved in fermentation, and the discovery of flavin (in yellow enzymes). Some sources report that he was selected to receive the award that year, but was prevented from receiving it by Adolf Hitler’s regime, which had issued a decree in 1937 that forbade Germans from accepting Nobel Prizes. According to the Nobel Foundation, this rumor is not true; although he was considered a worthwhile candidate, he was not selected for the prize at that time.