Cummings, J.A. and O.M. Smedstad, 2013: Variational data analysis for the global ocean. In: S.K. Park and L. Xu (Eds.), Data Assimilation for Atmospheric, Oceanic and Hydrologic Applications Vol. II., DOI 10.1007/978-3-642-35088-7_13, Springer-Verlag Berlin Heidelberg.