Bibliography:

1. ​ The Valuation of Unprotected Works: A Case Study of Public Domain Images on Wikipedia

2. ​ $2018

3. ​ Do Bad Things Happen When Works Enter the Public Domain?: Empirical Tests of Copyright Term Extension

4. Wikipedia Bibliography:

   1. ​ Wikimedia Commons

   2. ​ Statistical-Significance

   3. ​ Public Domain

   4. ​ https://en.wikipedia.org/wiki/Proxy_(statistics)