Whiteman, Digest of International Law, Department of State, Washington D.C., vol.
In addition, aside from the description by P.-H. Imbert himself (ibid., pp. 33-38), see M.M. Whiteman, Digest of International Law, Department of State, Washington, D.C., 1970, vol. 14, pp. 141-144 or J.M. Ruda, op.