A lot of Wiener's later work involved examining the genetics of the Rh factor. In the process, he became embroiled in controversy, as an alternative theory, the so-called CDE-nomenclature was proposed by Robert Russell Race and Ronald Fisher, hence also called Race-Fisher theory, which was somewhat simpler to understand. Although Wiener's theories on the genetics of the Rh factor have recently proven to be closer to the actual DNA structure of the genes (though the current scientific understanding combines aspects of the two theories), there are still many who have adopted the CDE notations.