V. Sobolev, T. Bazarova, N. Shugurova, N. Bazarov, Y. Dolgov, and H. Sørensen, “A preliminary examination of fluid inclusions in nepheline, sorensenite, tugtupite and chkalovite from the Ilímaussaq alkaline intrusion, South Greenland”, bullggu, vol. 81, pp. 1–41, Jan. 1970.