Gil Kalai
 Mailing address: 
Institute of Mathematics,
Hebrew University,
  Givat-Ram, Jerusalem 91904, Israel
 Telephone numbers: Office (972)2-6584729, Home (972)2-6536301, 
       Fax (972)2-5630702.
 Email addresses:  
kalai@math.huji.ac.il, 
  my home page
 Polytopes & Convexity
  An Invitation to Tverberg's Theorem 
We describe Tverberg theorem concerning point-configurations
in Euclidean spaces present Sarkria's striking proof and indicate
other proofs. We discuss topological generalization and questions 
related to the dimension of Tverberg points. In particular, we present
a 25-years old conjecture on the sum of the dimensions of tverberg 
points of all orders and speculate about applicability of this and 
related conjectures to graph coloring and the four color theorem.