<Tr> <Th> Effective </Th> <Td> 22 September 1988 </Td> </Tr> <Tr> <Th> Condition </Th> <Td> ratification by 20 states </Td> </Tr> <Tr> <Th> Signatories </Th> <Td> 28 </Td> </Tr> <Tr> <Th> Ratifiers </Th> <Td> 197 </Td> </Tr>

Vienna convention for the protection of the ozone layer signatories