Listen to Track 18.
Now answer the questions.
What is the lecture mainly about?
According to the professor, what is one problem with provenance?
Why does the professor talk about the 1930s Van Gogh forgery case in Berlin?
Why does the professor mention undocumented restorations?
The professor mentions four aspects of art authentication. Indicate the order in which they are presented in the lecture: first, second, third, or fourth.
Listen to Track 19.
Now answer the question.