Uwe Hohenstein Martin Gogolla A Calculus for an Extended Entity-Relationship Model Incorporating Arbitrary Data Operations and Aggregate Functions. 129-148 1988 ER db/conf/er/er88.html#HohensteinG88 conf/er/88 db/conf/er/HohensteinG88.html er88/ER88-P129.pdf conf/er/AtzeniBLV81 conf/er/AtzeniC81 conf/vldb/Bultzingsloewen87 books/el/Ceri83 conf/er/CampbellEC85 journals/tods/Chen76 conf/icde/Chen84 conf/tfais/DemoLG85 conf/er/SantosNF79 conf/er/EderK86 conf/er/ElmasriL85 ... conf/er/79 conf/er/81 conf/er/83 conf/er/85 conf/er/86 conf/er/ElmasriW81 journals/dke/ElmasriWH85 journals/tods/GogollaH91 ... conf/pods/JaeschkeS82 journals/jacm/Klug82 conf/er/LipeckN86 books/cs/Maier83 conf/er/MarkowitzR83 conf/er/MarkowitzR83a conf/vldb/MylopoulosW80 journals/tods/OzsoyogluOM87 conf/adbt/Pirotte77 ... conf/icde/ParentS84 journals/tse/ParentS85 conf/er/Roesner85 conf/er/Shoshani79 journals/tods/Shipman81 conf/er/SubietaM86 journals/is/Subieta87 journals/tods/SmithS77 journals/is/SchekS86 conf/vldb/SernadasSE87 conf/er/UrsprungZ83 conf/er/Velez85 conf/er/ZhangM83