When historians want to study the history of education, research, and knowledge itself, they often turn to the publications and notes of researchers and use them as primary sources.
It can seem counterintuitive to use journal articles and textbooks as primary sources--we usually think about these as secondary sources. However, think, for example, about how a history textbook from the 1920s is evidence of professional thinking and teaching during this time period.
When analyzing scholarly works as primary sources, consider the following:
To find the personal papers of a historical researcher, try searching Google Scholar for the researchers name with the additional keyword, "papers". Also use the OCLC FirstSearch (WorldCat) database to search by author to find published works by the researcher.