No stable currency zone has ever existed without mechanisms for raising taxes centrally and re-distributing them regionally.

BBC: Simpson: Bonfire of insanities

Given that, SNP ministers say, rUK ministers and the financial system would rationally prefer a stable sterling zone rather than Scotland deploying sterling free from constraint on their northern boundary.

BBC: Scottish independence: Political battle over currency

Britain wants a stable euro zone, but is torn.

ECONOMIST: Charlemagne

Nationalists say that, regardless of comments now, it would be very much in the interests of rUK (rest of the UK) to maintain a stable currency zone, including Scotland - not least because Scotland could use the pound unilaterally, without reference to London.

BBC: Malachi Malagrowther and the Scottish banknote

And there is one country that has historically said "non" to the transfers of sovereignty that might put the euro zone on a long-term stable footing: France.

WSJ: France Is Biggest Obstacle to Solution

If fiscal policy cannot be rehabilitated, adopting a target zone comes down to saying that stable currencies are worth the price of somewhat compromising the authorities' ability to use monetary policy in controlling inflation.

ECONOMIST: Off target

The Dutch economy is the fifth-largest economy in the euro-zone and is noted for its stable industrial relations, moderate unemployment and inflation, a sizable trade surplus, and an important role as a European transportation hub.

FORBES: Netherlands

Some economists, such as Klas Eklund at Skandinaviska Enskilda Banken, argue that Sweden's economy is in step with Europe, that interest rates set by the European Central Bank would suit it, and that the country would gain from a stable currency, more trade, higher growth and bigger markets within the euro zone.

ECONOMIST: Relations with the EU are warming a little

Fitch Ratings on Friday lowered its outlook on France's triple-A rating to "negative" from "stable" and warned that it is considering downgrading the debt of six of the countries in the euro zone.

WSJ: Euro Maintains $1.30 Level