Joints in graphs
  In 1969 Erdoes found a lower bound on the number of (r+1)-cliques sharing an edge in graphs with n vertices and t(r,n)+1 edges, where t(r,n) is the size of the Turan graph of order n and r color classes. We improve Erdoes's bound and prove a related stability result. 
B. Bollobas and V. Nikiforov