Lesson for Dasha 2
http://www.flickr.com/photos/kakissel/6165114664/in/photostream/http://www.3dprinter.net/reference/what-is-3d-printing
Prairie dog
http://newswatch.nationalgeographic.com/2014/01/07/video-why-do-prairie-dogs-do-the-wave/
History of English
http://ed.ted.com/lessons/how-did-english-evolve-kate-gardoqui