Curriculum.

There were a couple of papers missing in the `Teaching Materials` tab, which I have now added.

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Regarding exam question 4: From Niels Christian Juul's PhD thesis `juul_thesis.pdf`, read sections 1.3, 2.2 and 2.4 (you can skip the parts about reference counting).  Then, read the paper `copmrehensive_concurrent_robust_paper.pdf`. To test yourself, check that you understand the invariants in section 4.2 in the paper.