The Hyperfine Einstein-Infeld-Hoffmann Potential
  We use recently developed effective field theory techniques to calculate the third order post-Newtonian correction to the spin-spin potential between two spinning objects. This correction represents the first contribution to the spin-spin interaction due to the non-linear nature of general relativity and will play an important role in forthcoming gravity wave experiments. 
Rafael A. Porto, Ira Z. Rothstein