Rosana S. G. Lanzelotte Patrick Valduriez Mikal Ziane Jean-Pierre Cheiney Optimization of Nonrecursive Queries in OODBs. 1-21 1991 DOOD db/conf/dood/dood91.html#LanzelotteVZC91 http://dx.doi.org/10.1007/3-540-55015-1_1