@article{JGAA_2007_11_1_a0,
     author = {Patrick Healy and Karol Lynch},
     title = {Building {Blocks} of {Upward} {Planar} {Digraphs}},
     journal = {Journal of Graph Algorithms and Applications},
     pages = {3--44},
     publisher = {mathdoc},
     volume = {11},
     number = {1},
     year = {2007},
     doi = {10.7155/jgaa.00135},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.7155/jgaa.00135/}
}