Hirotaka Sakai A Unified Approach to the Logical Design of a Hierarchical Data Model. 61-74 1979 ER db/conf/er/er79.html#Sakai79 conf/er/79 db/conf/er/Sakai79.html er79/ER79-P061.pdf journals/tods/Chen76 conf/afips/Chen77 ... journals/tods/Delobel78 books/aw/Date77 conf/sigmod/MommensS75