[D] Interview for ML PhD – math related questions to expect?

Hello,

I have a (technical) interview for a PhD in ML coming up. I have been told to expect some questions on math and coding. For coding, I am preparing with LeetCode and TensorGym. However, I have no idea what to expect for math-related questions.

Anyone has an idea of what I can expect? Any useful resources? I can only find questions for Industry ML, and I don’t think they are useful for a PhD interview.

Thanks in advance.