Major Producers of Niobium Metal

Balliett, R.W. CosciA, M. HuNKELER, F.J. Niobium and tantalum in material selection. /. Metals, 38(9) (1986)25-32. 

Cabot Performance Material (1996) Cabot Technical Note No. 506-95-2.5M Niobium and Niobium Alloys. Boyertown, PA. 

Fairbrother, F. (1967) Chemistry of Niobium and Tantalum. Elsevier, New York. 

Hampel, C.A. (ed.) (1967) Rare Metals Handbook, 2nd ed. Reinhold, New York. 

(1988) High purity niobium for superconductor applications./. Less Common Metals, 139,149-158. 

---