Hans-Jörg Schek. Nested Relations, a Step Forward or Backward?. IEEE Data Eng. Bull., 11(3):56-63, 1988. [doi]
@article{Schek88, title = {Nested Relations, a Step Forward or Backward?}, author = {Hans-Jörg Schek}, year = {1988}, url = {http://sites.computer.org/debull/88SEP-CD.pdf}, researchr = {https://researchr.org/publication/Schek88}, cites = {0}, citedby = {0}, journal = {IEEE Data Eng. Bull.}, volume = {11}, number = {3}, pages = {56-63}, }