Class {@link toxTree.tree.cramer.CramerRules} is the implementation of Cramer rules [Cramer et al,78].
Cramer G. M., R. A. Ford, R. L. Hall, Estimation of Toxic Hazard - A Decision Tree Approach, J. Cosmet. Toxicol., Vol.16, pp. 255-276, Pergamon Press, 1978