SIMBAD references

A graphical technique for characterizing the light curves of RV Tauri variables is described. It is based on three measurements which are combined into two ratios plotted one against the other. Points that fall close together on the graph have similar light curves and also seem to share other properties in common (e.g.: period); this suggests that the technique might be useful for classifying members into subclasses. The scatter of points corresponding to individual cycles can be used as a measure of cycle regularity.