It had long been believed as a law that electrons and mobile ions migrate independently in a mixed ionic electronic conductor compound. It was found experimentally that it was only an exception: the interference effect between electrons and ions upon their transfer was not negligible; depending upon the thermodynamic state of the system. Also experimentally verified, with the highest-ever precision, was Onsager reciprocity in the phenomenon of mixed conduction in the solid state.

Onsager Coefficients of Mixed Ionic Electronic Conduction in Oxides. H.Yoo, D.K.Lee: Solid State Ionics, 2008, 179[21-26], 837-41