1. R. P. Bambah, V. C. Dumir and R. J. Hans-Gill: Non-homogeneous Problems: Conjectures of Minkowski and Watson in Number Theory, Indian National Science Academy, 2000, 15–41.
2. J. H. H. Chalk: On the positive values of linear forms, Quarterly J. Math. 18(1947), 215–227.
3. H. Davenport: Note on a result of Siegel, Acta Arithmetica 2(1937), 262–265.
4. H. Davenport: On the products of n linear forms, Proc. Camb. Phil. Soc. 49(1953), 190–193.
5. North-Holland Mathematical Library;P Gruber,1987