A one-stop source about multigenerational homes, ADU's, granny flats, backyard cottages, in-law units, accessory dwelling units…
ADUs have been the subject of academic and government study for several decades.
The searchable Space-Efficient Housing bibliography, housed at Zotero.org, attempts to maintain a complete record of formal research about ADUs and related topics such as demographic changes, the environmental impact of housing, etc. New contributors to that database are welcome.
We also link to current municipal codes and regulations here.