The CNO cycle<span> (for </span>carbon–nitrogen–oxygen<span>) is one of the two known sets of fusion reactions by which stars convert hydrogen to helium, the </span>other<span> being the proton–proton chain reaction. Unlike the latter, the CNO </span>cycle<span> is a catalytic </span>cycle<span>.</span>

. Iron is divalent to hydrogen and water.
Answer: Christine Herman & L.G Wade Jr., "2010". Organic Chemistry: Reaction of Alkane, 7e, Pearson Education, Radford University, Radford, VA.
Explanation:
This is an edited book. The Harvard reference style was used in the following order:
Authors name
Year of publication
Title
Edition
Publisher
Place of publication.
Note that the title of book should be italicized with capitalization of first word.
<span>The biogeochemical cycle that has the least activity because its essential element is mostly stored in rock is the phosphorus cycle. Phosphorus, unlike the other essential elements, is commonly found as a solid. This is why the atmosphere does not play a role in this cycle. Instead, phosphorus remains on land, and is mostly found in rocks and minerals.</span>