<Tr> <Td> 15 km </Td> <Td> N / A </Td> <Td> 1989--2003 </Td> </Tr> <Tr> <Td> 15--18 km </Td> <Td> 1925--Present </Td> <Td> N / A </Td> </Tr> <Tr> <Td> 20--30 km </Td> <Td> N / A </Td> <Td> 1978--Present </Td> </Tr> <Tr> <Td> 30 km </Td> <Td> 1926--Present </Td> <Td> N / A </Td> </Tr>

How long is the olympic cross country ski course