The 20th Conférence Générale des Poids et Mesures,
the results of the third periodic verification of national prototypes of the kilogram, which showed drifts, with respect to the international prototype, of the national prototypes and of the working copies and official copies held by the Bureau International des Poids et Mesures,
the fundamental impossibility of drawing definite conclusions from these results about the long-term stability of the international prototype and its copies,
the results of work in many national laboratories aimed at understanding the processes that lead to the instability of mass standards,
the progress now being made in various laboratories towards independent methods of monitoring the stability of mass standards,
recommends that national laboratories pursue their work on these experiments, and develop new ones, with a view to monitoring the stability of the international prototype of the kilogram and in due course opening the way to a new definition of the unit of mass based upon fundamental or atomic constants.