1Byrom, E.Ellis,D,E.,Freeman, A.J--Electronic Structure and Properties of Euo and EuS in the Molecular-Cluster Approximation. Pbys.Rev. B,1976,14:3558.
2Haselgrove, C.B.. The Numerical Approximation of Diophantus Method. Math. Comp., 1961,15:323.
3Midgley,C.M. The Crystal Structure of -Dicalcium Silicate. Acta Cryst. ,1952,5:307.