@article{10_4171_dm_473,
     author = {Piotr M. Hajac and Elmar Wagner},
     title = {The pullbacks of principal coactions},
     journal = {Documenta mathematica},
     pages = {1025--1060},
     year = {2014},
     volume = {19},
     doi = {10.4171/dm/473},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/dm/473/}
}