Sphere-of-influence graphs in normed spaces
  We show that any $k$-th closed sphere-of-influence graph in a $d$-dimensional normed space has a vertex of degree less than~$5^d k$, thus obtaining a common generalization of results of F\"uredi and Loeb (1994) and Guibas, Pach and Sharir (1994). 
M\'arton Nasz\'odi, J\'anos Pach and Konrad Swanepoel
math.MG