Bing found the following results
Duolingo
Duolingo Language Courses
Duolingo English Test
Duolingo: Learn Spanish, French and other languages for free
Duolingo: Language Lessons - Apps on Google Play
Duolingo: Language Lessons – Apps on Google Play
Duolingo Help Center
How to Use Duolingo for Language Learning
Duolingo
Duolingo - Language Lessons on the App Store