Input: Article: In addition to numerous articles on mathematics, Whitehead wrote three major books on the subject: A Treatise on Universal Algebra (1898), Principia Mathematica (co-written with Bertrand Russell and published in three volumes between 1910 and 1913), and An Introduction to Mathematics (1911). The former two books were aimed exclusively at professional mathematicians, while the latter book was intended for a larger audience, covering the history of mathematics and its philosophical foundations. Principia Mathematica in particular is regarded as one of the most important works in mathematical logic of the 20th century.

Now answer this question: What is the significance of Principia Mathematica currently?

Output: regarded as one of the most important works in mathematical logic of the 20th century

Input: Article: The onset of infrared is defined (according to different standards) at various values typically between 700 nm and 800 nm, but the boundary between visible and infrared light is not precisely defined. The human eye is markedly less sensitive to light above 700 nm wavelength, so longer wavelengths make insignificant contributions to scenes illuminated by common light sources. However, particularly intense near-IR light (e.g., from IR lasers, IR LED sources, or from bright daylight with the visible light removed by colored gels) can be detected up to approximately 780 nm, and will be perceived as red light. Sources providing wavelengths as long as 1050 nm can be seen as a dull red glow in intense sources, causing some difficulty in near-IR illumination of scenes in the dark (usually this practical problem is solved by indirect illumination). Leaves are particularly bright in the near IR, and if all visible light leaks from around an IR-filter are blocked, and the eye is given a moment to adjust to the extremely dim image coming through a visually opaque IR-passing photographic filter, it is possible to see the Wood effect that consists of IR-glowing foliage.

Now answer this question: What objects are notably bright in near IR?

Output: Leaves

Input: Article: The city went through serious troubles in the mid-fourteenth century. On the one hand were the decimation of the population by the Black Death of 1348 and subsequent years of epidemics — and on the other, the series of wars and riots that followed. Among these were the War of the Union, a citizen revolt against the excesses of the monarchy, led by Valencia as the capital of the kingdom — and the war with Castile, which forced the hurried raising of a new wall to resist Castilian attacks in 1363 and 1364. In these years the coexistence of the three communities that occupied the city—Christian, Jewish and Muslim — was quite contentious. The Jews who occupied the area around the waterfront had progressed economically and socially, and their quarter gradually expanded its boundaries at the expense of neighbouring parishes. Meanwhile, Muslims who remained in the city after the conquest were entrenched in a Moorish neighbourhood next to the present-day market Mosen Sorel. In 1391 an uncontrolled mob attacked the Jewish quarter, causing its virtual disappearance and leading to the forced conversion of its surviving members to Christianity. The Muslim quarter was attacked during a similar tumult among the populace in 1456, but the consequences were minor.

Now answer this question: When did Valencia suffer from the Black Death?

Output:
1348