A portion of the literature that you will find in urban studies is made up of reports, white papers, and more. These materials are referred to as grey literature because they are not commercially published. Rather, this literature is published by non-profits, research agencies, governments, etc. It can be helpful to supplement your searches by looking at institutional and agency web sites, and by searching databases containing citations to working papers.
Watch this two-minute video for a brief introduction to grey literature from Western University.