<a href="https://en.wikipedia.org/wiki/Carbon_cycle" class="extiw" title="en:Carbon cycle">Carbon Cycle</a>
Diagram adapted from U.S. DOE, Biological and Environmental Research Information System.
<a rel="nofollow" class="external free" href="http://earthobservatory.nasa.gov/Features/CarbonCycle/">http://earthobservatory.nasa.gov/Features/CarbonCycle/</a>