@misc{eppel_a_multigrid_1990, 
author={Eppel, D. P., Callies, U.},
title={A multigrid approach for variational data assimilation into hyperbolic model equations},
year={1990},
howpublished = {conference lecture: Clermont-Ferrand (F);},
note = {Eppel, D.; Callies, U.: A multigrid approach for variational data assimilation into hyperbolic model equations. In: International Symposium on Assimilation of Observations in Meteorology and Oceanography. Clermont-Ferrand (F). 1990. 37-41.}}