1. Schnöcke, H.: Neues Jahrb. Mineral., Abhandl. 106 (1967) 1–54.
2. Semenov, E.I., in: Mineralogy of the Ilimaussaq Alkaline Massif, Southern Greenland; Inst. Mineral. Geokhim. Kristallokhim. Redkilch Elementov, Izdat "Nauka" 1969, 96–97; Am. Mineralogist 55 (1970) 2139 (Referat).
3. Yoder jr., H.S., Eugster, H.P.: Geochim. Cosmochim. Acta 8 (1955) 225–280.
4. Heinrich, E.W., Levinson, A.A.: Am. Mineralogist 40 (1955) 983–995.
5. Pabst, A.: Am. Mineralogist 40 (1955) 967–974.