Yosuke Sasaki Hitoshi Yamasaki Takayoshi Shoudai Tomoyuki Uchida Mining of Frequent Block Preserving Outerplanar Graph Structured Patterns. 239-253 2007 ILP http://dx.doi.org/10.1007/978-3-540-78469-2_24 conf/ilp/2007 db/conf/ilp/ilp2007.html#SasakiYSU07