Hitohiro Shiozaki Tomonobu Ozaki Takenao Ohkawa Mining Closed and Maximal Frequent Induced Free Subtrees. 14-18 2006 conf/icdm/2006w ICDM Workshops http://doi.ieeecomputersociety.org/10.1109/ICDMW.2006.111 db/conf/icdm/icdmw2006.html#ShiozakiOO06