@article{10_4171_dm_399,
     author = {Dragos Oprea},
     title = {Framed sheaves over treefolds and symmetric obstruction theories},
     journal = {Documenta mathematica},
     pages = {323--342},
     year = {2013},
     volume = {18},
     doi = {10.4171/dm/399},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/dm/399/}
}