Extensions of maps to the projective plane
arXiv:math/0410370 · doi:10.2140/agt.2005.5.1711
Abstract
It is proved that for a 3-dimensional compact metrizable space X the infinite real projective space is an absolute extensor of X if and only if the real projective plane is an absolute extensor of X.
Published by Algebraic and Geometric Topology at http://www.maths.warwick.ac.uk/agt/AGTVol5/agt-5-69.abs.html