diff --git a/src/include/serif/dimensions/dimensions.hpp b/src/include/serif/dimensions/dimensions.hpp
index 8f683e0d..060251a1 100644
--- a/src/include/serif/dimensions/dimensions.hpp
+++ b/src/include/serif/dimensions/dimensions.hpp
@@ -54,6 +54,26 @@ namespace serif::dimensions {
         static constexpr std::string_view identifier = "time";
     };
 
+    /**
+     * @struct InverseTimeSquared
+     *
+     * @brief Inverse time squared, the physical dimension of a Poisson residual.
+     */
+    struct InverseTimeSquared final : PhysicalQuantity
+    {
+        static constexpr std::string_view identifier = "inverse_time_squared";
+    };
+
+    /**
+     * @struct GravitationalConstant
+     *
+     * @brief Newton's gravitational constant, expressed in the selected system of units.
+     */
+    struct GravitationalConstant final : PhysicalQuantity
+    {
+        static constexpr std::string_view identifier = "gravitational_constant";
+    };
+
     /**
      * @struct Area
      *