Answer:
The topic of historical research by Helen Yoshida was 'Department of Justice (DOJ) camps during World War II.'
Step-by-step explanation:
Helen Yoshida is a writer, oral historian, and World War 2 history explorer. When in 2010, Yoshida was trying to research for her topic for her thesis, she came too know about the Department of Justice that incarcerated more than 30,000 people during the World War 2, which includes Japanese, Italian, Central Americans, and Germans. She began to interview people who were incarcerated and the families of those who were incarcerated.
Thus, her topic of research was 'DOJ camps during WWII.'