Leen Lambers Hartmut Ehrig Ulrike Prange Fernando Orejas Embedding and Confluence of Graph Transformations with Negative Application Conditions. 162-177 2008 ICGT http://dx.doi.org/10.1007/978-3-540-87405-8_12 conf/gg/2008 db/conf/gg/icgt2008.html#LambersEPO08