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Duolingo, Inc.
Screenshot
File:Duolingo homepage.png
Duolingo homepage
Type of businessPrivate
Available in
HeadquartersPittsburgh, Pennsylvania, United States
Area servedWorld
Founder(s)Luis von Ahn, Severin Hacker
CEOLuis von Ahn
IndustryOnline education, Professional certification, Translation, Crowdsourcing
ServicesLanguage courses, Duolingo English Test, Duolingo for Schools, Tinycards flashcard app
Revenue36 million USD in 2018[1]
Employees200+[2]
URLwww.duolingo.com
AdvertisingYes
RegistrationYes
Users±300 million users[3]
Launched30 November 2011; 12 years ago (2011-11-30) (private beta)
19 June 2012; 12 years ago (2012-06-19) (public release)
Current statusOnline
Native client(s) onAndroid, iOS, Windows Phone, Windows 10 Mobile
Written inSwift,[4] React, Python, Scala[5]HTML, CSS, JavaScript

Duolingo (/ˌduːoʊˈlɪŋɡoʊ, djuː-, dʒuː-/ D(Y)OO-oh-LING-goh) is an American platform that includes a language-learning website and mobile app, as well as a digital language-proficiency assessment exam. The company uses the freemium model; the app and the website are accessible without charge, although Duolingo also offers a premium service for a fee.

As of 30 June 2020, the language-learning website and app offers 95 different language courses in 38 languages. The app has over 300 million registered users across the world.[7][8][9][10]

History

2010–2019 logo

The project was started at the end of 2009 in Pittsburgh by Carnegie Mellon University professor Luis von Ahn (creator of reCAPTCHA) and his graduate student Severin Hacker, and then developed along with Antonio Navas, Vicki Cheung, Marcel Uekermann, Brendan Meeder, Hector Villafuerte, and Jose Fuentes.[11][12][13]

Inspiration for Duolingo came from two places. Luis Von Ahn wanted to create another program that served two purposes in one, what he calls a "twofer".[14] Duolingo originally did this by teaching its users a foreign language while having them translate simple phrases in documents, though the translation feature has since been removed.[15]

Von Ahn was born in Guatemala and saw how expensive it was for people in his community to learn English. Severin Hacker (born in Zug, Switzerland), co-founder of Duolingo and current CTO, and Von Ahn believe that "free education will really change the world"[16] and wanted to supply people an outlet to do so.

The project was originally sponsored by Luis von Ahn's MacArthur fellowship and a National Science Foundation grant.[17][18]

On October 19, 2011, during in its "Early Stage Venture" stage Duolingo raised $3.3 million from a Series A first-round of funding, led by Union Square Ventures, with participation from author Tim Ferriss and actor Ashton Kutcher's firm, A-Grade Investments [19][20][21]

Duolingo launched into private beta a month later on November 30, 2011, and accumulated a waiting list of more than 300,000 users.[22][23][13]

On June 19, 2012, Duolingo later launched for the general public.[24]

On September 17, 2012, while still in its "Early Stage Venture" stage, Duolingo raised $15 million from a Series B second-round of funding led by New Enterprise Associates, with participation from Union Square Ventures bringing Duolingo's total funding to $18.3 million.[25]

On 13 November 2012, Duolingo released their iOS app through the iTunes App Store.[26] The application is a free download and is compatible with most iPhone, iPod and iPad devices.[27]

On 29 May 2013, Duolingo released their Android app, which was downloaded about a million times in the first three weeks and quickly became the #1 education app in the Google Play store.[28]

On June 19, 2013, one year after launching for the general public, Duolingo passed 4 million users, all through word of mouth,[29] and on November 21, 2013, Duolingo reached 15 million users[29]

On February 18, 2014, Duolingo entered its "Late Stage Venture" stage, and raised $20 million from a Series C third-round of funding led by Kleiner Caufield & Byers.[30] It was reported Duolingo had about 25 million registered users, 12.5 million active users, and 34 employees.[31] On June 2, 2014, Duolingo passed 30 million users[29]

On June 10, 2015, Duolingo raised $45 million from a Series D fourth-round of funding led by Google Capital, bringing its total funding to $83.3 million, a valuation of $470 million, as well as passing 100 million users.[32][33][34]

In April 2016 it was reported that Duolingo had 17 million monthly users.[35][36]

On July 25, 2017, that Duolingo raised $25 million from a Series E fifth-round of investment from Drive Capital, bringing its total funding to $108.3 million, a valuation of $700 million, as well as passing 200 million users and having 25 million monthly users.[37][38] It was reported that Duolingo had 95 employees,[39] and the funds would be directed toward creating initiatives such as TinyCards and Duolingo Labs.[40]

On August 1, 2018, it was reported Duolingo passed 300 million users.[41]

On December 4, 2019, it was announced that Duolingo raised $30 million in a series F sixth-round of investment from Alphabet’s investment company CapitalG, bringing a total funding of $138.3 million, a valuation of $1.5 billion, reporting 30 million monthly active learners.[42] Duolingo will use the funds on developing new products and expanding its team. Expanding the team will span a variety of positions, including in engineering, business development, design, curriculum and content creators, community outreach and marketing.[43]

During 2019, Duolingo grew from 170 staff members[44] to 200 employees,[39] with headquarters in the Pittsburgh neighborhood of East Liberty[45][46][47] and offices in New York; Bellevue, Washington (near Seattle); and Beijing.[39][48] Of Duolingo’s 200 employees, 166 work in its East Liberty headquarters, 17 work in New York, 8 in Bellevue, and 8 in China.[43]

Duolingo had a revenue of $1 million in 2016, $13 million in 2017,[41] $36 million in 2018,[44] and is projected to hit $86 million in 2019.[49]

Business model

Most language-learning features in Duolingo are free of charge, but it uses periodic advertising in both its mobile and web browser applications,[50][51] which users can remove by paying a subscription fee. This feature, which is named ‘Duolingo Plus’, includes benefits such as unlimited hearts, level skipping, and progress quizzes. It originally employed a crowd sourced business model, where the content came from organizations (such as CNN and BuzzFeed) that paid Duolingo to translate it.[52]

Infrastructure

Duolingo uses many services in the Amazon Web Services suite of products, including Amazon DynamoDB, Amazon Virtual Private Cloud, nearly 200 virtual instances in Amazon Elastic Compute Cloud (EC2), Amazon Simple Storage Service (S3) and Amazon Relational Database Service (RDS).[53] The server backend is written in the programming language Python.[better source needed] A component called the Session Generator was rewritten in Scala by 2017.[5] The frontend was written in Backbone.js and Mustache but is now primarily in React and Redux. Duolingo provides a single-page web application for desktop computer users and also smart phone applications on Android (both Google Play Store and Amazon Appstore), iOS App Store and Windows Phone platforms. 20% of traffic comes from desktop users and 80% from mobile app users.[53]

Duolingo's mascot, a green cartoon owl named Duo, has been a subject of an Internet meme in which the mascot will stalk and threaten users if they do not keep using the app.[54] Acknowledging the meme, Duolingo released a video on April 1, 2019 as an April Fools' Day joke; the video depicts a fictitious new premium feature called "Duolingo Push". In the video, users of "Duolingo Push" will receive reminders to use the app in person by Duo himself, who stares at users and follows them around until they use the app (in the video, Duo is depicted by a person in a large mascot costume).[55][56]

In November 2019, Saturday Night Live parodied Duolingo in a skit where adults learned to communicate with children using a fictitious course on the app titled "Duolingo for Talking to Children".[57]

Recognition and awards

In 2013, Apple chose Duolingo as its iPhone App of the Year, the first time this honor had been awarded to an educational application.[58] Duolingo won Best Education Startup at the 2014 Crunchies,[45] and was the most downloaded app in the Education category in Google Play in 2013 and 2014.[59] In 2015, Duolingo was announced the 2015 award winner in Play & Learning category by Design to Improve Life.[60]

Duolingo was named No. 44 on Fast Company's "The World's 50 Most Innovative Companies" list in 2018 "for making new languages irresistible".[61] No. 2 on Fast Company's "The World's Most Innovative Companies: Education Honorees" in 2018 "for making a new language irresistible",[62] and No. 2 on Fast Company's "The World's Most Innovative Companies: Education Honorees" in 2017 "for letting friends compare notes as they learn a new language".[63] No. 6 on Fast Company's "The World's Most Innovative Companies: Social Media Honorees" in 2017 "for letting friends compare notes".[64] No. 7 on Fast Company's "The World's Most Innovative Companies: Education Honorees" in 2013 "for crowdsourcing web translation by turning it into a free language-learning program".[65]

Duolingo won Inc. magazine's Best Workplaces 2018,[66] Entrepreneur magazine's Top Company Culture List 2018,[67] and appeared in CNBC's 2018 and 2019 "Disruptor 50" lists.[68][69][70] TIME Magazine's 50 Genius Companies.[71] In 2019, Duolingo was named one of Forbes's "Next Billion-Dollar Startups 2019".[72]

Features

Presentation at Wikimania about Duolingo.

Duolingo mimics the structure of video games in several ways in order to engage its users. It features a reward system in which users acquire "lingots", an in-game currency that they can spend on features such as character customizations or bonus levels (both available on the mobile app only).

On public leaderboards people can compete against their friends or see how they stack up against the rest of the world. The level system that Duolingo uses is XP (experience points), a numerical system that represents a user's skill-level. Badges in Duolingo represent achievements that are earned from completing specific objectives or challenges.[73]

The study process in Duolingo combines various methods such as: listening to the pronunciation, reading sentences, voice recording, forming phrases by ordering words and matching images to words.[74]

Use in schools

Duolingo provides "Duolingo for Schools" with features designed to allow teachers to track their students. In 2012 an effectiveness study concluded that Duolingo usage for Spanish study was more effective than classroom language-learning alone, but that Duolingo was less effective for advanced language-learners.[75] One proposed reason for this is that the grammar-translation method that Duolingo primarily uses is more applicable to simple words and phrases than to complex ones; simpler ones can translate in a more exact manner from one language to another and thus are more conducive to Duolingo's grammar-translation method.[76]

Criticism

Duolingo has received criticism for its lack of effectiveness in helping students to fully learn a language. Duolingo CEO, Luis von Ahn, promises only to get users to a level between advanced beginner and early intermediate: 'A significant portion of our users use it because it's fun and it's not a complete waste of time'. After six months of studying French with Duolingo, von Ahn demonstrated a lack of basic verb tenses when asked to describe his weekend in French, "mangling his tenses." Bob Meese, Duolingo's chief revenue officer, did not immediately understand the spoken question "¿Hablas español?" after six months of Duolingo Spanish study.[1]

Language coach and Podcaster Kersten Cable has criticized the app for "its impractical vocabulary, its insistence upon one acceptable translation per sentence prompt, and its lack of explanation for incorrect answers"[77] describing the Duolingo's method as "you learn by parroting phrases without even beginning to cover the background stories that grammar and pragmatics tell."[78] Linguist Steven Sacco at the San Diego State university attempted to test Duolingo's claim of "34 hours of Duolingo are equivalent to a full university semester of language education"[79] by completing a course in Swedish and taking a standardized elementary exam ultimately receiving a failing grade.[77] Sacco suggested some use for Duolingo as helpful for learning vocabulary only in addition to immersion environments like a classroom.[77] Both Sacco and Cable added that Duolingo's translation method of teaching is ultimately inferior to learning language in an immersion environment.

Language courses

Courses for English speakers

As of 24 June 2020, 36 courses are available to the public in English, three of which are constructed languages, and those three include two fictional languages.[80][81][82] In this list, the courses are ordered by number of active learners.

Complete

Beta

Alpha

As of 24 June 2020, three courses for English speakers are in development (ordered by progression percentage towards completion according to the Weekly Incubator Update[89])

Courses available in other languages

As of 28 June 2020, the following languages are available to speakers of languages other than English:[93]

(#) = course still in development (β) = Course still in beta version

Number of languages available for speakers of 'x' language on the app and on the website

Rank
Number of languages
available for speakers of:		 On app On website
1 English 36 39 (Haitian Creole, Maori and Yiddish in the incubator)
2 Spanish 10 12 (Yucatec and K'iche in incubator)
3 Chinese 6 7 (German in incubator)
4 Portuguese 6 6
5 French 5 6 (Esperanto in beta)
6 Arabic 4 5 (Spanish in incubator)
7 Russian 4 5 (Swedish in incubator)
8 Turkish 3 5 (French and Swedish in incubator)
9 Italian 3 (Spanish not available on app) 4
10 German 3 3
11 Japanese 2 2
12 Dutch 2 3 (French in incubator)
13 Czech 1 1
14 Greek 1 1
15 Hindi 1 1
16 Hungarian 1 2 (German in incubator)
17 Indonesian 1 1
18 Korean 1 1
19 Polish 1 1
20 Romanian 1 1
21 Thai 1 1
22 Ukrainian 1 1
23 Vietnamese 1 1
24 Bengali – 1 (English in incubator)
25 Punjabi (Gurmukhi) – 1 (English in incubator)
26 Tagalog – 1 (English in incubator)
27 Tamil – 1 (English in incubator)
28 Telugu – 1 (English in incubator)

List of courses by number of learners

As of March 2020, 94 courses are available to start learning, and 10 are available to be notified when they are released.[103]

Rank Teaching For Speakers of Number of Learners Release date[104]
1 English Spanish 27,600,000[105] 2012-03-30 – 30 March 2012
2 Spanish English 24,200,000[106] 2011-11-30 – 30 November 2011
3 French English 13,600,000[107] 2012-06-19 – 19 June 2012
4 English Portuguese 10,800,000[108] 2012-10-30 – 30 October 2012
5 German English 7,820,000[109] 2011-11-30 – 30 November 2011
6 Japanese English 6,430,000[110] 2017-05-18 – 18 May 2017
7 English Russian 5,720,000[111] 2015-11-02 – 2 November 2015
8 Italian English 5,300,000[112] 2012-11-13 – 13 November 2012
9 English Arabic 4,520,000[113] 2014-05-09 – 9 May 2014
10 English French 4,430,000[114] 2013-05-07 – 7 May 2013
11 French Spanish 3,880,000[115] 2014-01-10 – 10 January 2014
12 Korean English 3,670,000[116] 2017-10-10 – 10 October 2017
13 Chinese English 3,560,000[117] 2017-11-15 – 15 November 2017
14 Russian English 3,300,000[118] 2015-11-02 – 2 November 2015
16 English Chinese 3,190,000[119] 2014-04-11 – 11 April 2014
15 English Turkish 3,050,000[120] 2013-12-29 – 29 December 2013
17 Spanish Portuguese 2,650,000[121] 2014-03-09 – 9 March 2014
18 Italian Spanish 2,510,000[122] 2014-09-15 – 15 September 2014
19 English German 2,280,000[123] 2013-11-27 – 27 November 2013
20 Portuguese English 2,240,000[124] 2012-10-30 – 30 October 2012
21 English Vietnamese 2,150,000[125] 2014-06-10 – 10 June 2014
22 English Italian 2,120,000[126] 2012-11-24 – 24 November 2012
23 Portuguese Spanish 2,110,000[127] 2014-02-01 – 1 February 2014
24 English Polish 1,660,000[128] 2014-01-19 – 19 January 2014
25 German Spanish 1,590,000[129] 2014-05-19 – 19 May 2014
26 English Hindi 1,520,000[130] 2014-04-21 – 21 April 2014
27 Turkish English 1,450,000[131] 2013-12-29 – 29 December 2013
28 Spanish French 1,430,000[132] 2014-05-21 – 21 May 2014
29 Arabic English 1,410,000[133] 2019-06-25 – 25 June 2019
30 French Portuguese 1,400,000[134] 2015-03-12 – 12 March 2015
31 Dutch English 1,350,000[135] 2014-07-16 – 16 July 2014
32 Swedish English 1,190,000[136] 2014-11-17 – 17 November 2014
33 English Japanese 1,170,000[137] 2014-03-03 – 3 March 2014
34 English Indonesian 1,140,000[138] 2014-04-23 – 23 April 2014
35 Spanish German 1,080,000[139] 2015-09-01 – 1 September 2015
36 Hindi English 1,070,000[140] 2018-07-18 – 18 July 2018
37 Greek English 1,040,000[141] 2016-08-30 – 30 August 2016
38 Japanese Chinese 958,000[142] 2019-04-24 – 24 April 2019
39 English Romanian 942,000[143] 2014-02-04 – 4 February 2014
40 Irish English 924,000[144] 2014-08-25 – 25 August 2014
41 German Russian 887,000[145] 2014-03-26 – 26 March 2014
42 English Dutch 879,000[146] 2013-12-23 – 23 December 2013
43 Polish English 877,000[147] 2015-12-10 – 10 December 2015
44 High Valyrian English 875,000[148] 2017-07-12 – 12 July 2017
45 Norwegian English 841,000[149] 2015-05-21 – 21 May 2015
46 Hebrew English 814,000[150] 2016-06-21 – 21 June 2016
47 English Czech 803,000[151] 2014-10-17 – 17 October 2014
48 Italian Portuguese 765,000[152] 2017-06-13 – 13 June 2017
49 French Arabic 761,000[153] 2016-02-02 – 2 February 2016
50 French German 750,000[154] 2014-03-31 – 31 March 2014
51 English Hungarian 713,000[155] 2014-01-08 – 8 January 2014
52 Russian Spanish 706,000[156] 2018-06-20 – 20 June 2018
53 Catalan Spanish 679,000[157] 2015-11-19 – 19 November 2015
54 Latin English 676,000[158] 2019-08-28 – 28 August 2019
55 German Portuguese 669,000[159] 2015-09-15 – 15 September 2015
56 English Korean 632,000[160] 2014-05-26 – 26 May 2014
57 French Russian 620,000[161] 2016-02-18 – 18 February 2016
58 Vietnamese English 583,000[162] 2016-04-21 – 21 April 2016
59 English Ukrainian 565,000[163] 2014-08-12 – 12 August 2014
60 Italian French 562,000[164] 2014-11-06 – 6 November 2014
61 Korean Chinese 559,000[165] 2019-04-24 – 24 April 2019
62 Hawaiian English 554,000[166] 2018-10-05 – 5 October 2018
63 German French 550,000[167] 2015-10-14 – 14 October 2015
64 Spanish Russian 544,000[168] 2016-03-02 – 2 March 2016
65 German Turkish 538,000[169] 2015-12-14 – 14 December 2015
66 Danish English 506,000[170] 2014-08-25 – 25 August 2014
67 Romanian English 438,000[171] 2016-11-15 – 15 November 2016
68 Czech English 416,000[172] 2017-09-05 – 5 September 2017
69 Spanish Chinese 406,000[173] 2016-07-06 – 6 July 2016
70 German Arabic 392,000[174] 2016-03-07 – 7 March 2016
71 Welsh English 389,000[175] 2016-01-26 – 26 January 2016
72 Indonesian English 387,000[176] 2018-08-15 – 15 August 2018
73 French Italian 364,000[177] 2015-10-08 – 8 October 2015
74 Swahili English 358,000[178] 2017-02-20 – 20 February 2017
75 Klingon English 344,000[179] 2018-03-15 – 15 March 2018
76 English Thai 337,000[180] 2017-05-10 – 10 May 2017
77 German Italian 316,000[181] 2017-01-09 – 9 January 2017
78 Hungarian English 314,000[182] 2016-06-30 – 30 June 2016
79 Ukrainian English 308,000[183] 2015-05-21 – 21 May 2015
80 Russian Turkish 293,000[184] 2018-02-08 – 8 February 2018
81 Navajo English 292,000[185] 2018-10-05 – 5 October 2018
82 Esperanto English 282,000[186] 2015-05-28 – 28 May 2015
83 Portuguese French 279,000[187] 2017-01-30 – 30 January 2017
84 English Greek 255,000[188] 2014-04-25 – 25 April 2014
85 Esperanto Spanish 254,000[189] 2016-10-26 – 26 October 2016
86 Guarani Spanish 250,000[190] 2016-08-30 – 30 August 2016
87 French Chinese 237,000[191] 2019-04-24 – 24 April 2019
88 Esperanto Portuguese 216,000[192] 2018-05-15 – 15 May 2018
89 Scottish Gaelic English 167,000[193] 2019-11-27 – 27 November 2019
90 Swedish Arabic 147,000[194] 2016-03-01 – 1 March 2016
91 Italian Chinese 83,800[195] 2019-04-24 – 24 April 2019
92 Spanish Italian 68,800[196] 2018-08-22 – 22 August 2018
93 Chinese Japanese 48,500[197] 2019-11-21 – 21 November 2019
94 Swedish Spanish 31,000[198] 2019-11-30 – 30 November 2019
95 German Dutch 19,300[199]

List of courses in beta

As of 7 May 2020, 7 courses are in the beta phase on Duolingo.[200] Date courses started development were obtained from the Duolingo Wiki.[201]

Rank Teaching For Speakers of Number of Learners Date courses started development Release date into Beta
1 Korean Chinese 1,090,000[202] 2018-09-10 – 10 September 2018 2019-04-24 – 24 April 2019
2 Spanish Chinese 423,000[203] 2016-07-06 – 6 July 2016 2018-06-25 – 25 June 2018
3 Hungarian English 319,000[204] 2014-03-12 – 12 March 2014 2016-06-30 – 30 June 2016
4 Klingon English 317,000[205] 2015-04-09 – 9 April 2015 2018-03-15 – 15 March 2018
5 Navajo English 286,000[206] 2018-08-23 – 23 August 2018 2018-10-05 – 5 October 2018
6 Esperanto Portuguese 207,000[207] 2017-03-13 – 13 March 2017 2018-05-15 – 15 May 2018
7 Italian Chinese 136,000[208] 2018-09-10 – 10 September 2018 2019-04-24 – 24 April 2019

List of courses being created

As of 24 June 2020, 20 courses are currently being developed on Duolingo.[200] Percentages are based on jrikhal's Weekly Incubator Summary.[209]

Rank by
Estimated
Completion 		Teaching For
Speakers of 		Percent
completed 		Date courses started
development [201] 		Estimated
completion date 		Number of Contributors
1 English Tamil 82% 2016-06-01 – 1 June 2016 2020-08-01 – 1 August 2020 2[210]
2 English Bengali 79% 2016-06-02 – 6 June 2016 2022-02-21 – 21 February 2022 2[211]
3 Yiddish English 78% 2015-02-19 – 19 February 2015 2020-12-31 – 31 December 2020 9[212]
4 Swedish Russian 66% 2015-02-18 – 18 February 2015 2021-04-24 – 24 February 2021 0[213]
5 English Tagalog 49% 2016-08-30 – 30 August 2016 2020-09-01 – 1 September 2020 2[214]
6 Spanish Arabic 30% 2016-09-12 – 12 September 2016 9999-12-31 – 31 December 9999 3[215]
7 English Punjabi (Gurmakhi) 29% 2016-12-08 – 8 December 2016 2019-07-08 – 8 July 2019 2[216]
8 Esperanto French 2020-07-01 – 1 July 2020 10[217]
9 French Turkish 28% 2015-10-27 – 27 October 2015 2022-02-19 – 19 February 2022 0[218]
10 English Telugu 22% 2016-08-10 – 10 August 2016 2019-12-25 – 25 December 2019 2[219]
11 Finnish English 18% 2019-04-17 – 17 April 2019 2020-12-31 – 31 Decemberl 2020 7[220]
12 Haitian Creole English 18% 2017-01-27 – 27 January 2017 2020-07-01 – 1 July 2020 5[221]
13 French Dutch 2020-12-20 – 20 December 2020 9[222]
14 Esperanto Chinese 2020-05-06 – 6 May 2020 12[223]
15 Māori English 1% 2020-02-12 – 12 February 2020 2021-02-21 – 21 February 2021 3[224]
16 German Hungarian 0.5% 2019-06-18 – 18 June 2019 2020-03-25 – 25 March 2020 5[225]
17 Italian German 0.25% 2021-03-12 – 12 March 2021 2[226]
18 German Chinese 0% 2018-09-10 – 10 September 2018 2020-06-30 – 30 June 2020 1[227]
19 English Hebrew 0% 2019-11-03 – 3 November 2019 2020-04-12 – 12 April 2020 0[228]
20 Yucatec Spanish 0% 2020-02-12 – 12 February 2020 2021-02-12 – 12 February 2021 4[229]
21 K'iche' Spanish 0% 2020-02-12 – 12 February 2020 2021-02-12 – 12 February 2021 0[229]
 USA  Spain  France  Germany  Italia  Japan  South Korea  China  Russia  Portugal  Turkey  Netherlands  Sweden  Ireland  Greece  Israel  Poland  Norway  Catalonia  Vietnam  Denmark  Romania  Tanzania   Esperanto  Hungary   Klingon  Paraguay  Wales  Ukraine  India  Czech Republic  Hawaii  Indonesia  Saudi Arabia
German x
Arabic x
Bengali
Czech x
Chinese x
Korean x
Spanish x
French x
Greek x
Hindi x
Hungarian x
Indonesian x
English x
Italian x
Japanese x
Dutch x
Punjabi
Polish x
Portuguese x
Romanian x
Russian x
Tagalog
Tai
Tamil
Telugu
Turkish x
Ukrainian x
Vietnamese x

See also

References

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