User:Reidbrown0605/Nitrogen fixation/Bibliography

You will be compiling your bibliography and creating an outline of the changes you will make in this sandbox.

Outline of proposed changes

 * Adding Rhizobia as an example diazotrophic bacteria (done, in beginning section before history subsection)
 * Discuss when nitrogenase was thought to have evolved
 * How certain is this?
 * Different forms (MoFe, FeFe, VFe) and what influences which form
 * What environmental conditions gave rise to nitrogenase evolving