@article{DOCMA_2014__19__a18,
     author = {Graf, Patrick and Kov\'acs, S\'andor J.},
     title = {An optimal extension theorem for 1-forms and the {Lipman-Zariski} conjecture},
     journal = {Documenta mathematica},
     pages = {815--830},
     publisher = {mathdoc},
     volume = {19},
     year = {2014},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/DOCMA_2014__19__a18/}
}