41.   These one unit changes are known as single nucleotide polymorphisms, or SNPs, and are a principal source of human genetic variation.

42.   This reliably unnatural river is the principal source of drinking water in Kansas City and St. Louis.

43.   Those accounts were promptly denied by the Cuban government, which relies on tourism as its principal source of hard currency.

44.   TV Critic Ken Parish Perkins reports on how CNBC has become the principal source of business and financial news.

45.   In fact, the General Assembly, and not the Security Council, should be the principal source of power and authority within the UN system.

46.   Japan is the principal source of capital around the world.

47.   Liquidation of the mine will mean that this isolated border area will lose its principal source of revenue.

48.   Principal source of the Jordan river.

49.   The Golden Crescent, nickname for the Afghanistan-Pakistan border area, remains the principal source area for morphine and heroin reaching Europe, the report said.

50.   The principal source of attrition was Romario.