<mp-units/framework/reference_concepts.h>
template<
typename T,
auto QS>
concept ReferenceOf = Reference<T> && QuantitySpec<MP_UNITS_REMOVE_CONST(decltype(QS))> &&
QuantitySpecOf<decltype(get_quantity_spec(T{})), QS>;
Satisfied by all references for which QuantitySpecOf<QS>
is true.