@article{10_2140_agt_2003_3_117,
     author = {Apostolakis, Nikos},
     title = {On 4{\textendash}fold covering moves},
     journal = {Algebraic and Geometric Topology},
     pages = {117--145},
     year = {2003},
     volume = {3},
     number = {1},
     doi = {10.2140/agt.2003.3.117},
     url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2003.3.117/}
}