It's a paper of 1959!!. You can find more information in the bookNumerical Solution of Multidimensional Gas Dynamics Problems, edited by S. K. Godunov (Nauka, Moscow,1976) [In Russian]; Résolution numerique des problèmes multidimensionnels de la dynamiqe des gas,edited by S. Godunov (Mir, Moscow, 1979). [In French]And to have an idea about how the master discovered the method, you canget the JCP paper "Reminiscences about Difference Schemes", Sergei Konstantinovich GodunovJournal of Computational Physics, pages 6-25,available online at
www.scd.ucar.edu/css/staff/flyer/godunov.pdf Farid.