@article{10_4171_dm_465,
     author = {Patrick Graf and S\'andor J. Kov\'acs},
     title = {An optimal extension theorem for 1-forms and the {Lipman{\textendash}Zariski} conjecture},
     journal = {Documenta mathematica},
     pages = {815--830},
     year = {2014},
     volume = {19},
     doi = {10.4171/dm/465},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/dm/465/}
}