With Alexander Wiener he discovered another blood factor, labeled the Rh factor, for Rhesus monkeys, in which the factor was first discovered.

Objective To evaluate the role of endothelium-derived hyperpolarizing factor (EDHF) in flow-dependent coronary vasodilation induced by reactive hyperemia (RH).

Rh blood-group system: system for classifying blood according to presence or absence of the Rh antigen (factor) in erythrocytes.