Schematic diagram of <a href="https://en.wikipedia.org/wiki/A.C._Kirk" class="extiw" title="en:A.C. Kirk">A.C. Kirk</a>'s <a href="https://en.wikipedia.org/wiki/oil_shale" class="extiw" title="en:oil shale">oil shale</a> retort, in wide use during the late 1800s.
<a href="//commons.wikimedia.org/wiki/User:Splette" title="User:Splette">Thomas Splettstoesser</a>
CC BY-SA 3.0
<p>Own work  using:
</p>
<ul><li>Text and diagrams: <a rel="nofollow" class="external free" href="http://www.iom-world.org/pubs/IOM_TM8502.pdf">http://www.iom-world.org/pubs/IOM_TM8502.pdf</a> pp. 56-57</li>
<li>See also: Louw, S.J.; Addison, J. (1985). Seaton, A. (ed.). "Studies of the Scottish oil shale industry. Vol.1 History of the industry, working conditions, and mineralogy of Scottish and Green River formation shales. Final report on US Department of Energy" (PDF). Historical Research Report. Institute of Occupational Medicine: 35, 38, 56–57. DE-ACO2 – 82ER60036. Archived from the original (PDF) on 2011-07-26. Retrieved 2009-06-05.</li></ul>