Edmodo also has document libraries on class subjects where teachers can share materials with other teachers.

FORBES: Edmodo Nabs $15 Million From Benchmark, Greylock For Educational Technology

In 2001, book authors and the Authors Guild filed a class-action lawsuit, as did publishers, alleging that Google had violated copyright laws by scanning books from the libraries of major universities without always getting permission from the copyright owners of the books.

BBC: Judge delays Google books hearing