1. Adachi, G. (ed.) (2008) Handbook of Rare Earth Elements in Material Engineering. NTS Inc., Tokyo (in Japanese).
2. Arai, H. and Machida, M. (1996) Thermal stabilization of catalyst supports and their application to high-temperature catalytic combustion. Appl. Catal., A 138, 161-176.
3. Aubert, D., Le Roux, G., Krachler, M., Cheburkin, A., Kober, B., Shotyk, W. and Stille, P. (2006) Origin and fluxes of atmospheric REE entering an ombrotrophic peat bog in Black Forest (SW Germany): Evidence from snow, lichens and mosses. Geochim. Cosmochim. Acta 70, 2815-2826.
4. Bau, M. and Dulski, P. (1996) Anthropogenic origin of positive gadolinium anomalies in river waters. Earth Planet. Sci. Lett. 143, 245-255.
5. Center for Global Environmental Research National Institute for Environmental Studies (2009) (http://db.cger.nies.go.jp/metex/trajectory.html), accessed July 2010.