Use the library's catalog, Worldcat to search for primary sources in the MSJC collections. The material in the MSJC collections are assigned specific subject terms by the Library Congress. These terms can assist you in finding primary sources on your topic. Examples include:
If you don't find the content you need in the MSJC libraries' collection, you can use Worldcat to search libraries worldwide! Just change the "limit results" drop down menu to libraries worldwide. You are now searching libraries all over the world including the UC libraries, many of the Cal State collections and 1000's of other research libraries.