But the economy, he said, "is a persistent source of discontent," unlike the other two, which can ebb and flow depending on daily events.

Though for some, the persistent and escalating sources of sound can often be considered an annoyance.

Ending the restrictions would eliminate a persistent source of friction between the two countries.

Her fingertips were a persistent, rhythmic source of pleasure.

Is there a persistent source of irritation?

The absence of modern literary conventions, which are an aid to comprehension, was an early and persistent source of errors affecting transmission of the text.

The price for medical care, a persistent source of worry for Americans and their employers, jumped 4.3 percent last year.

The relationship between father and son has been a major pillar of sports as well as a persistent source of unhappiness and frustration.

This awkward (and sometimes arbitrary) split of responsibilities is a persistent source of organisational stress.

The province's periodic issuance of paper currency was also a persistent source of friction between factions in the province, due to its inflationary effects.