1. Hastad's 3-bit PCP and hardness of max-3sat: Notes of Subhash Khot Link
2. Hardness of Minimum distance of code: Link
3. Hardness of edge-disjoint path: Link
4. Asymmetric k-center hardness: Link
5. Inapproximability of Hypergraph Vertex Cover: Link
6. Hardness of priority Steiner tree: Link1 and Link2
7. Hardness of machine minimization problem: Link
8. Hardness of buy at bulk network design: Link
9. UGC: Link