@article{10_2140_agt_2005_5_1711,
     author = {Dydak, Jerzy and Levin, Michael},
     title = {Extensions of maps to the projective plane},
     journal = {Algebraic and Geometric Topology},
     pages = {1711--1718},
     year = {2005},
     volume = {5},
     number = {4},
     doi = {10.2140/agt.2005.5.1711},
     url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2005.5.1711/}
}