But for bonds to rally, buying may have to appear from some unconventional source.

If you counted unconventional sources (the carbon content is much harder to calculate), the proportion would be even smaller.

And there are also unconventional sources as well.

A California utility is hoping to replace power once generated by a nuclear reactor with energy from unconventional sources.

Thus a variety of minerals and metals are obtainable from unconventional sources with resources available in huge quantities.

Not all the artists in the show get their images from such unconventional sources.

Information from unconventional sources not related to the industry carries the extra burden of having to be proved relevant or urgent.

That's when I turned to a more unconventional source of financial wisdom.

A study by Wood Mackenzie suggests that within 15 years all the world's extra oil supply is likely to come from unconventional sources.

As oil prices rise, unconventional sources become economically viable.