Key points are not available for this paper at this time.
DAVID HOFFMAN is Professor of Mathematics and Co-Director of the Geometry, Analysis, Numerics and Graphics Center (GANG) at the University of Massachusetts, Amherst. He earned his Ph.D. in mathematics at Stanford, after receiving undergraduate degrees at the University of Rochester (in history and mathematics). He has pursued research and/or teaching at the Universities of Durham and Warwick (UK), Michigan and Stanford, as well as IMPA (Rio de Janeiro, Brazil) and the University of Paris VII. He is the 1990 recipient of the MAA Chauvenet Prize.
Hoffman et al. (Mon,) studied this question.