Priestley, J (1772). "Observations on Different Kinds of Air". Philosophical Transactions of the Royal Society of London. 62. London: Phil. Trans. Roy. Soc.: 147–264. doi:10.1098/rstl.1772.0021. S2CID186210131.
van Niel, C. B. (1931). "On the morphology and physiology of the purple and green sulfur bacteria". Arch. Microbial. 3: 1–114. doi:10.1007/BF00454965. S2CID19597530.
Priestley, J (1772). "Observations on Different Kinds of Air". Philosophical Transactions of the Royal Society of London. 62. London: Phil. Trans. Roy. Soc.: 147–264. doi:10.1098/rstl.1772.0021. S2CID186210131.
van Niel, C. B. (1931). "On the morphology and physiology of the purple and green sulfur bacteria". Arch. Microbial. 3: 1–114. doi:10.1007/BF00454965. S2CID19597530.