1. Introduction and historical background; 2. The simplest upper bound for G(k); 3. Goldbach's problems; 4. The major arcs in Waring's problem; 5. Vinogradov's methods; 6. Davenport's methods; 7. Vinogradov's upper bound for G(k); 8. A ternary additive problem; 9. Homogenous equations and Birch's theorem; 10. A theorem of Roth; 11. Diophantine inequalities; 12. Wooley's upper bound for G(k); Bibliography.