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There are no dedicated IPA symbols for degrees of aspiration and typically only two degrees are marked: unaspirated ⟨k⟩ and aspirated ⟨kʰ⟩. An old symbol for light aspiration was ⟨ʻ⟩, but this is now obsolete. The aspiration modifier letter may be doubled to indicate especially strong or long aspiration. Hence, the two degrees of aspiration in Korean stops are sometimes transcribed ⟨kʰ kʰʰ⟩ or ⟨kʻ⟩ and ⟨kʰ⟩, but they are usually transcribed [k] and [kʰ], with the details of voice-onset time given numerically.

What language, according to the text, may need double stops to indicate aspiration length?
Answer: Korean
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These immigrants were largely responsible for the first general strike in North America in 1835, in which workers in the city won the ten-hour workday. The city was a destination for thousands of Irish immigrants fleeing the Great Famine in the 1840s; housing for them was developed south of South Street, and was later occupied by succeeding immigrants. They established a network of Catholic churches and schools, and dominated the Catholic clergy for decades. Anti-Irish, anti-Catholic Nativist riots had erupted in Philadelphia in 1844. In the latter half of the century, immigrants from Russia, Eastern Europe and Italy; and African Americans from the southern U.S. settled in the city. Between 1880 and 1930, the African-American population of Philadelphia increased from 31,699 to 219,559. Twentieth-century black newcomers were part of the Great Migration out of the rural South to northern and midwestern industrial cities.

When did the black population explode?
Answer: Between 1880 and 1930
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Eritrea is a multilingual country. The nation has no official language, as the Constitution establishes the "equality of all Eritrean languages". However, Tigrinya serves as the de facto language of national identity. With 2,540,000 total speakers of a population of 5,254,000 in 2006, Tigrinya is the most widely spoken language, particularly in the southern and central parts of Eritrea. Modern Standard Arabic and English serve as de facto working languages, with the latter used in university education and many technical fields. Italian, the former colonial language, is widely used in commerce and is taught as a second language in schools, with a few elderly monolinguals.

What is the official language of Eritrea?
Answer:
The nation has no official language