<Tr> <Td> 17th </Td> <Td> 1965 </Td> <Td> 9th </Td> <Td> 1965 </Td> </Tr> <Tr> <Td> 18th </Td> <Td> 1971 </Td> <Td> 10th </Td> <Td> 1971 </Td> </Tr> <Tr> <Td> 19th </Td> <Td> 1979 </Td> <Td> 11th </Td> <Td> 1979 </Td> </Tr> <Tr> <Td> 20th </Td> <Td> </Td> <Td> 12th </Td> <Td> </Td> </Tr>

First order of division of classes in ddc is based on