||Kihara S, Hartzler DA, Savikhin S. Oxygen concentration inside a functioning photosynthetic cell. Biophys J. 2014 May 6 106(9):1882-9. doi: 10.1016/j.bpj.2014.03.031 p.1887 right column 3rd paragraphPubMed ID24806920
|| F.S. Rowland Stratospheric Ozone Depletion C. Zeferos, G. Contopoulos, E. Flores (Eds.), Twenty Years of Ozone Decline, Springer, New York (2006), pp. 23-66
||P.1887 right column 3rd paragraph: "An additional factor influencing the growth of the first cyanobacteria could have been ozone generated by solar radiation, since the stratosphere of Archaean Earth lacked an ultraviolet-blocking ozone layer (ref 64). However, the ratio of ozone to oxygen in the stratosphere of present-day Earth only reaches ∼5 × 10^−5 (primary source), which amounts to an average of ∼0.05 molecules of ozone per cell of Gloeobacter violaceus, an amount that is hardly of significance (assuming an oxygen concentration of 0.02 μM)."