It is impossible for the species to be a viable population by natural reproduction.

BBC: Earth News - Giant fish 'verges on extinction'

This lends weight to the theory that a viable hybrid population was sustained by interbreeding over a long time.

ECONOMIST: Humans could have interbred with chimpanzees

Ranchers say the wolves prey on their livestock, and they argue that the program is unnecessary because there is already a viable wolf population in the area.

CNN: Appeals court ruling protects wolves in Yellowstone

It's certainly large enough to be a viable political unit: The District's population is greater than Wyoming's by some 50, 000 people, and by square mileage it would be about the size of New Jersey.

FORBES

The NIH said the scientists who developed these stem cells lines have told the agency that the stem cells are viable and can be frozen and cultured and have been through more than one population doubling.

CNN: NIH announces owners of stem cells

TV3 says it can be received by 90% of the Irish population, and will extend its transmission network when it is "financially viable".

BBC: Irish fans miss Street

Among the working population, few potential employees had the education and skills necessary to support a viable business enterprise.

FORBES: Mobile Afghanistan: How A National Telecom Network Delivers Social Goods

He argues that mobile penetration in America is unlikely to grow as fast as it did in Japan and Europe because population density is much lower there, making it harder to set up economically viable networks.

ECONOMIST: Who’s the real winner? | The

To coincide with a booming population, Boston sports owners have made savvy investments that have turned the city into an extremely viable sports culture.

FORBES: Sports Is Helping To Spur Growth In Boston