1. D. Kirkpatrick , Proc. Conf. Light Met., Anaheim, CA, USA, 1996, pp. 75–80
2. C. Fernandez , J.Ayala, F.Blanco, J. J.del Campo and P.Garcia, Proc. Conf. Light Met., Anaheim, CA, USA, 1996, pp. 99–106
3. R. Kanev , D.Chavdarova and L.Silla, Proc. 6th Yugosl. Int. Symp. Alum., Bauxites and Extractive Metallurgy, Titovo Uzice, Yugoslavia, 1990, pp. 18–20
4. M. G. Sujana , B. C.Acharya, S. N.Das, S. B.Rao and R. S.Thakur, Proc. Conf. Light Met., Anaheim, CA, USA, 1996, pp. 93–98
5. V. Mymrin and I.Pininsca, Stratto da Geol. Applic. E Idrogeologia, Bari, Italia, XIII, 1978, pp. 293–298