Tomonobu Ozaki Takenao Ohkawa Mining Mutually Dependent Ordered Subtrees in Tree Databases. 75-86 2008 PAKDD Workshops http://dx.doi.org/10.1007/978-3-642-00399-8_7 conf/pakdd/2008w db/conf/pakdd/pakdd2008w.html#OzakiO08a