You are looking for primary sources of Urie Brofenbrenner

You can search our databases by author.  If for example, you are looking for his original works for example, "ecological systems theory" or "ecology of human development,"  you can check our Psychology databases. Choose Database Finder from the library home page, and then search in PsychArticles, or ProQuest Central.  You can also use Google Scholar.  

A primary document in this instance will be a report on the original work he has done, so look for articles authored by him, rather than books that describe the subject and mention him in the text.  To be primary it has to be written by him, or to have co-authors.  The article should also describe the research, perhaps an investigation. Perhaps there will be a control group and likely some reference to statistical relevance.