<Tr> <Td> 08 </Td> <Td> Walker, Texas Ranger </Td> <Td> CBS </Td> <Td> 1993 - 04 - 21 </Td> <Td> 2001 - 05 - 19 </Td> <Td> 201 </Td> </Tr> <Tr> <Td> 08 </Td> <Td> The Cosby Show </Td> <Td> NBC </Td> <Td> 1984 - 09 - 20 </Td> <Td> 1992 - 04 - 30 </Td> <Td> 201 </Td> </Tr> <Tr> <Td> 08 </Td> <Td> That' 70s Show </Td> <Td> FOX </Td> <Td> 1998 - 08 - 23 </Td> <Td> 2006 - 05 - 18 </Td> <Td> 200 </Td> </Tr> <Tr> <Td> 08 </Td> <Td> Who's the Boss? </Td> <Td> ABC </Td> <Td> 1984 - 09 - 20 </Td> <Td> 1992 - 04 - 25 </Td> <Td> 196 </Td> </Tr>

What is the longest running tv series in the us