Historically within the Reformed tradition there have been two distinctly different approaches to the doctrine of the Covenant of Grace, which in modern times may perhaps best be understood by comparing two lectures on this subject. One was given by Klaas Schilder in the Netherlands for those who had followed him in the Liberation in 1944 shortly after the 2nd World War, and the other by Herman Hoeksema in a conference with the men of the German Reformed Churches in 1945. Both were given in distinctly different situation, but address essentially the same subject, as can be seen by activating the following links:
Schilder in August, 1944, The Main Points Of The Doctrine of the Covenant
Hoeksema in September 1945: The Idea of the Covenant