Simmons, A.J., Jones, P.D., da Costa Bechtold, V., Beljaars, A.C.M., Kallberg, P.W., Saarinen, S.M., Viterbo, P. and Wedi, N., 2004
Comparison of trends and variability in CRU, ERA-40 and NCEP/NCAR analyses of monthly-mean surface air temperature.
ERA-40 Project Report Series 18 38pp ECMWF, Reading, UK