@article{RenSigmanMeckleretal.2009,
  author    = {Haojia Ren and Daniel M. Sigman and Anna Nele Meckler and Birgit Plessen and Rebecca S. Robinson and Yair Rosenthal and Gerald H. Haug},
  title     = {Foraminiferal isotope evidence of reduced nitrogen fixation in the Ice Age Atlantic ocean},
  doi       = {10.1126/science.1165787},
  url       = {http://www.sciencemag.org/},
  year      = {2009},
}