Any topic (writer’s choice)
Here are some resources:
https://www.vam.ac.uk/articles/architects-and-their-sketchbooks
http://www.vam.ac.uk/content/articles/a/architects-sketchbooks/
https://www.bloomberg.com/news/articles/2012-03-02/the-official-guide-to-tactical-urbanism
https://issuu.com/streetplanscollaborative/docs/tactical_urbanism_vol_2_final?e=4528751/2585800
https://www.cityfabrick.org/