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. 2020 Sep 28;378(2183):20190314. doi: 10.1098/rsta.2019.0314

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© 2020 The Authors.

Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.

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Figure 2. — The decline in SO₂ and smoke in London following the Clean Air Act (1956), including data from the ‘bubbler method’ sampling air through a peroxide solution in water and ultraviolet (UV) spectroscopy. (M. L. Williams, personal communication, 2017). (Online version in colour.)