Gabriel Baum Silvia E. Gordillo Claudia Pons Clara Smith Carlos A. Tau Conceptual Layers in an Object Oriented Database. An Unified Model. 141-147 DASFAA93/P141.pdf 1993 DASFAA db/conf/dasfaa/dasfaa93.html#BaumGPST93 conf/dasfaa/93 db/conf/dasfaa/BaumGPST93.html conf/oodbs/AlbanoGOO86 conf/sigmod/CareyDV88 books/aw/kimL89/FishmanABCCDHHKLLMNRSW89 books/aw/kimL89/KimBCGW89 conf/sigmod/KimBG89 conf/sigmod/LecluseRV88 journals/tcs/Wirsing86 conf/esec/WirsingHS89