International Committee for Weights and Measures
The International Committee for Weights and Measures states: "In order to avoid any risk of confusion between the absorbed dose "D" and the dose equivalent "H", the special names for the respective units should be used, that is, the name gray should be used instead of joules per kilogram for the unit of absorbed dose "D" and the name sievert instead of joules per kilogram for the unit of dose equivalent "H"."