building floor plans and blueprints in U.S.

[archistudier]

I am doing a research project on Southern California architecture that blends commercial and residential use in single complexes and need to use floor plans from existing buildings in the Los Angeles and San Diego area. Does anyone know who to speak to dirtectly to obtain copies of these floor plans/blueprints and if so what the general procedure usually is? Any and all help would be appreciated, thanks.