In 1966 Australian scientists M. D. Hatch and C. R. Slack described the pathway of carbon assimilation in the light neutral phase of photosynthesis called the Hatch-Slack cycle. They proved that the first stable compound produced in photosynthesis was four-carbon oxaloacetic acid (OAA). Hence it is called C4 cycle. This cycle is also known as dicarboxylic cycle. In 1970, it was recognized as Hatch-Slack cycle. In 1965, Hugo Kortschak, Hart and George Burr first observed that oxaloacetic acid was the first stable substance produced during CO2 oxidation in sugarcane leaves. The cycle is also called the HSK pathway because scientists Hatch, Slack and Kortschak discovered the series of reactions in the C4 pathway. Currently, this pathway has been discovered in many plants of 16 genera.