There are two significant publications by one of them reads as Seck HA (1971b) Der Einfluss des Drucks auf die Zusammensetzung koexistierender Alkalifeldsp€ate und Plagioklase im System NaAlSi3O8–KAlSi3O8–CaAl2Si2O8–H2O. in Contrib Mineral Petrol 31: 67–86.
They are related to feldspar geothermometry.
Does anyone possess these two publications with translated versions in English? Can you share?