Problem: I know that the answer to the question "Which are there more of, residents in Center City or public parks?" is in "Philadelphia's central city was created in the 17th century following the plan by William Penn's surveyor Thomas Holme. Center City is structured with long straight streets running east-west and north-south forming a grid pattern. The original city plan was designed to allow for easy travel and to keep residences separated by open space that would help prevent the spread of fire. The Delaware River and Schuylkill Rivers served as early boundaries between which the city's early street plan was kept within. In addition, Penn planned the creation of five public parks in the city which were renamed in 1824 (in parenthesis): Centre Square, North East Publick Square (Franklin Square), Northwest Square (Logan Square), Southwest Square (Rittenhouse Square), and Southeast Square (Washington Square). Center City has grown into the second-most populated downtown area in the United States, after Midtown Manhattan in New York City, with an estimated 183,240 residents in 2015.". Can you tell me what it is?

A: residents

Problem: I know that the answer to the question "What was written in the 30th year of the 19th century?" is in "Four boarders at his parents' apartments became Chopin's intimates: Tytus Woyciechowski, Jan Nepomucen Biaobocki, Jan Matuszynski and Julian Fontana; the latter two would become part of his Paris milieu. He was friendly with members of Warsaw's young artistic and intellectual world, including Fontana, Jozef Bohdan Zaleski and Stefan Witwicki. He was also attracted to the singing student Konstancja Gadkowska. In letters to Woyciechowski, he indicated which of his works, and even which of their passages, were influenced by his fascination with her; his letter of 15 May 1830 revealed that the slow movement (Larghetto) of his Piano Concerto No. 1 (in E minor) was secretly dedicated to her "It should be like dreaming in beautiful springtime by moonlight." His final Conservatory report (July 1829) read: "Chopin F., third-year student, exceptional talent, musical genius."". Can you tell me what it is?

A: his letter

Problem: I know that the answer to the question "This work was not characterized as portraying formal economics by Friedman?" is in "Hayek is widely recognised for having introduced the time dimension to the equilibrium construction and for his key role in helping inspire the fields of growth theory, information economics, and the theory of spontaneous order. The "informal" economics presented in Milton Friedman's massively influential popular work Free to Choose (1980), is explicitly Hayekian in its account of the price system as a system for transmitting and co-ordinating knowledge. This can be explained by the fact that Friedman taught Hayek's famous paper "The Use of Knowledge in Society" (1945) in his graduate seminars.". Can you tell me what it is?

A: Free to Choose

Problem: I know that the answer to the question "what time period is mentioned last?" is in "In the mid-19th century, Serbian (led by self-taught writer and folklorist Vuk Stefanovic Karadzic) and most Croatian writers and linguists (represented by the Illyrian movement and led by Ljudevit Gaj and uro Danicic), proposed the use of the most widespread dialect, Shtokavian, as the base for their common standard language. Karadzic standardised the Serbian Cyrillic alphabet, and Gaj and Danicic standardized the Croatian Latin alphabet, on the basis of vernacular speech phonemes and the principle of phonological spelling. In 1850 Serbian and Croatian writers and linguists signed the Vienna Literary Agreement, declaring their intention to create a unified standard. Thus a complex bi-variant language appeared, which the Serbs officially called "Serbo-Croatian" or "Serbian or Croatian" and the Croats "Croato-Serbian", or "Croatian or Serbian". Yet, in practice, the variants of the conceived common literary language served as different literary variants, chiefly differing in lexical inventory and stylistic devices. The common phrase describing this situation was that Serbo-Croatian or "Croatian or Serbian" was a single language. During the Austro-Hungarian occupation of Bosnia and Herzegovina, the language of all three nations was called "Bosnian" until the death of administrator von Kallay in 1907, at which point the name was changed to "Serbo-Croatian".". Can you tell me what it is?

A:
1907