<Dd> <Ul> <Li> 1950s </Li> <Li> 1960s </Li> <Li> 1970s </Li> <Li> 1980s </Li> <Li> 1990s </Li> </Ul> </Dd> <Ul> <Li> 1950s </Li> <Li> 1960s </Li> <Li> 1970s </Li> <Li> 1980s </Li> <Li> 1990s </Li> </Ul> <Dd> Retrocession to China </Dd> <Dd> Hong Kong since 2000 </Dd>

Which of the following was not a provision of the treaty of nanjing in 1842