From the Cultural Landscape Foundation's page about St. Francis Square's landscaping history and design: https://tclf.org/landscapes/st-francis-square
From the JSTOR Daily (a digital library, JSTOR stands for Journal Storage), the history about how the union built St. Francis Square: https://daily.jstor.org/st-francis-square-affordable-housing-san-francisco/
From DOCOMOMO/NOCA (Northern California Chapter, Documentation and Conservation of buildings, sites, and neighborhoods of the modern movement), architectural focus on St. Francis Square: http://docomomo-noca.org/buildings/st-francis-square/
From the Western Edition, a neighborhood newspaper, a story about the 50th anniversary of St. Francis Square: http://www.thewesternedition.com/?c=117&a=2525
From the Online Archive of California SFSQ page: https://oac.cdlib.org/findaid/ark:/13030/c8154ff8/entire_text/ This site describes in some detail the archival collection containing records and publications donated by SFSQ founders and shareholders between 1957 and 2010 and maintained at the San Francisco public library.