Citric acid in intermediate metabolism in animal tissues.

Citric acid cycle (CAC) of aerobic carbohydrate metabolism (Krebs cycle). Three months after his initial publication on CAC Krebs published a supplementary paper aimed at the medical audience, rather than the biochemical audience that read Enzymologia:  "The intermediate metabolism of carboyhdrates," Lancet, 230 (1937) 736-41.

In 1953 Krebs shared the Nobel Prize in Physiology or Medicine with Fritz Lipmann (No. 751.3) "for discovery of the citric acid cycle."

(Thanks to Juan Weiss for recommending the supplementary paper.)