Bibliography/My list of sources, each from my research about my topic:

For my underground rap album/mixtape covers: https://www.dazeddigital.com/music/article/34911/1/hip-hop-mixtape-cover-art-book

For my mainstream rap album/mixtape covers: https://medium.com/@bradcallas/the-15-best-hip-hop-album-covers-of-all-time-5b0031b6571d