How racist policing took over American cities, explained by a historian 

https://www.vox.com/2020/6/6/21280643/police-brutality-violence-protests-racism-khalil-muhammad?bblinkid=231158783&bbemailid=22839843&bbejrid=1556814559

Alisa Sarah Kramer, “William H. Parker and the Thin Blue Line: Politics, Public Relations, and Policing in Postwar Los Angeles,” PhD. Dissertation, American University, 2007 

https://dra.american.edu/islandora/object/thesesdissertations%3A3293/datastream/PDF/view