Machkour, Mustapha, Karim Afdel, and Youness Idrissi Khamlichi. 2014. “Conversion Methodology from Hierarchical Model to Objectrelational Model With Structural and Semantic Aspects Preservation”. International Journal Of Mathematics And Computer Research 2 (07), 503-11. https://ijmcr.in/index.php/ijmcr/article/view/156.