On the Vitamin Content of Cod Liver Oil, as Influenced by the Nutritional State of the Cod. E. Poulsson and F. Ender. State Vitamin Institute, Oslo. Skandinavisches Archiv. für Physiologie, Vol. 66, 1933, p. 92.

From these experiments the conclusion can be drawn, that the liver oil from the spawning, mal-nourished cod contains a somewhat smaller amount of vitamin A but considerably more vitamin D than does the liver oil from the well-nourished, not spawning cod.