『Abstract
　The increase in the oxidation state of the atmosphere during Earth history is well documented, but not the reasons for this process. The course of atmospheric evolution has been dominated by the effects of photosysthesis and by the composition of volcanic gases. The H2/H2O ratio of volcanic gases has remained essentially constant during most of Earth history. It is here proposed that their CO2/H2O and SO2/H2O ratios have increased with time. A simple model for the degassing and the recycling of CO2, SO2, and H2O can account for many of the major steps in the oxygenation of the atmosphere.』

1. Introduction
2. First-order model
3. Testing and refining the model
　3.1. The Archean CO2 flux
　3.2. Te Archean SO2 flux
　3.3. The Archean excess hydrogen flux
　3.4. The timing of the crossover
　3.5. The Great Oxidation Event
　3.6. The Boring Billion, Snowball Earths, and the Phanerozoic
4. Assessment and conclusions
Acknowledgments
References