>https://www.amazon.de/gp/feature.html?ie=UTF8&docId=1000854623&ref_=mas_surl_undrgrnd&pf_rd_m=A3JWKAKR8XB7XF&pf_rd_s=nav-sitewide-msg&pf_rd_r=16XC42HFSF7ZBGAGFF7G&pf_rd_t=4201&pf_rd_p=684684827&pf_rd_i=navbar-4201
>
>http://techcrunch.com/2015/08/26/amazon-underground-is-an-android-app-store-with-only-actually-free-apps/