For references we refer to
Al-Sharrah, G. 2014. Ranking Hazarduous Chemicals with a Heuristic Approach to Reduce Isolated Objects in Hasse Diagrams. Pages 217-235 in R. Bruggemann, L. Carlsen, and J. Wittmann, eds. Multi-indicator Systems and Modelling in Partial Order. Springer, New York.
Al-Sharrah, G. 2010. Ranking Using the Copeland Score: A Comparsion with the Hasse Diagram. J.Chem.Inf.Model. 50:785-791.