"principle sources" is correct and usable in written English.
You can use it to refer to the main sources of information that you rely on in a research or academic paper. For example, "This paper draws from two principle sources: the works of Smith and Jones."
Their principle sources of income have remained the same for centuries, through ranching, farming and jewelry making.
One of the principle sources of petroleum demand is the transportation sector, which primarily consumes petrol or diesel.
Maybe it should: Social Ads is likely to be one of the company's principle sources of revenue.
A cursory conclusion from these results could indicate that frustrations derive from two principle sources: lack of efficiency in service tasks, and staff having less than sunny personalities.
Landless households engaged in agriculture and marginal agricultural households earn the lion share of their income from the factor market for 'illiterate-agricultural workers' whereas the non-agricultural households with high-skilled labor earn more than 90%% of their income from the 'high-skill labors' and 'capital markets' as their principle sources of income.
In my novel, "Mother of the Believers," I discuss how the Prophet's wife Aisha was a scholar who was fluent in the Quran, as well as a jurist, who served as one of the principle sources of Islamic law and teachings.
The zoomorphism of items from the broom cupboard becomes a principle source of delight.
The principle source of those infections was the same as that for polio: rotten sanitation.
Physical disabilities accounted for 80.1% of all reported disability, with its principle source being health- related.
"For some time, the UK economy has relied on domestic consumers as the principle source of growth.
ER: I have some ideas in the shower, but my principle source for those ideas is walking.
