@misc{claussen_estimation_of_1991, 
author={Claussen, M.},
title={Estimation of areally-averaged surface fluxes},
year={1991},
howpublished = {GKSS report},
note = {Claussen, M.: Estimation of areally-averaged surface fluxes. Boundary Layer Meteorology. 1991. vol. 54, 387-410.}}