1. V. P. Naumenko and L. M. Razdorskih, Issledovanii v oblasti ohrani okruzayushtey sredy, Trudy NIUIF, 239 (1981) 22.
2. A. A. Akhberdin et al., Fizicheskie Svoystva Rasplavov Systemy CaO-SiO2-Al2O3-MgO-CaF2, Moskva Metallurgia, 1987, p. 7.
3. L. P. Vijsimaa, A. A. M. Kuusk and P. O. Kuusyk, Termicheskii Analiz Fosfogypsa, Trudy Tallinskogo Polytekhnicheskogo Instituta, 479 Tallin (1979) 29.
4. Iv. Dombalov, Iv. Gruncharov, Y. Pelovski and G. Bechev, IVth Polish Sem. to the memory of Prof. Bretsznajder, Plock, 17–19. 9. 1986, p. 83.
5. Iv. Gruncharov, G. Bechev, Iv. Dombalov and Y. Pelovski, God. VMGI-Sofia, 17 (1983) 143.