A DBMS Prototype to Support Extended NF2 Relations: An Integrated View on Flat Tables and Hierarchies. - Peter Dadam; Klaus Küspert; F. Andersen; Henk M. Blanken; R. Erbe; Jürgen Günauer; Vincent Y. Lum; Peter Pistor; Georg Walch (SIGMOD Conference, 1986)

Designing A Generalized NF2 Model with an SQL-Type Language Interface. - Peter Pistor; F. Andersen (VLDB, 1986)