Comparison of Categorical Foundations of Object-Oriented Database Model. - Tomas Hruska; Petr Kolencik (DOOD, 1997)

Extending an Object-Oriented Model: Multiple Class Objects. - Tomas Hruska; Petr Kolencik (ER, 1997)

Behavioral Safety in a Model With Multiple Class Objects. - Tomas Hruska; Petr Kolencik; Michal Mácel (SOFSEM, 1998)